€¦ · Contents Declaration Abstract Acknowledgements List of Symbols Nomenclature 1 Introduction...
118
Ultra-Wideband Phased Array Radar for Short-Range Imaging Applications Pei-Yu Chao A thesis submitted to the Department of Electrical Engineering, University of Cape Town, in fulfillment of the requirements for the degree of Master of Science in Engineering. Cape Town, June 2009
Transcript of €¦ · Contents Declaration Abstract Acknowledgements List of Symbols Nomenclature 1 Introduction...
Ultra-Wideband Phased Array Radar for Short-Range Imaging Applications
Pei-Yu Chao
A thesis submitted to the Department of Electrical Engineering,
University of Cape Town, in fulfillment of the requirements
for the degree of Master of Science in Engineering.
Cape Town, June 2009
The copyright of this thesis vests in the author. No quotation from it or information derived from it is to be published without full acknowledgement of the source. The thesis is to be used for private study or non-commercial research purposes only.
Published by the University of Cape Town (UCT) in terms of the non-exclusive license granted to UCT by the author.
Contents
Declaration
Abstract
Acknowledgements
List of Symbols
Nomenclature
1 Introduction
1.1 Introduction to Ultra-Wideband Radar ................. .
1.2 Background....................
1.3 Objectives............
1.4 Limitations and scope of thesis .
1.5 Thesis Outline. . . . . . . . . .
2 Literature Review
2.1 Ultra-Wideband Wavefonns
2.1.1 Impulse (Short Pulse)
2.1.2 Chirp (Linear Frequency Modulation)
2.1.3 Step-Frequency Wavefonn .
2.2 Past Work in UWB Impulse Radar .
2.3 Ultra-Wideband Impulse Array System
2.4 Applications ofUWB Impulse Array in Radar . .
2.4.1 Non-Destructive Evaluation
2.4.2 Through-Wall Imaging ...
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2.5 Existing Signal-Channel UWB radar at University of Cape Town. 14
3 Ultra-wideband System Overview 19
3.1 Design Specifications .... . .. . .. .. . . . .. .. . .. .. .. 19
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7.3.3 Range Resolution Test . . . . . . . . 91
7.3.4 UWB Phased Array Beamforming . . 93
7.3.5 Through Wall Detection - Wall thickness 93
7.3.6 Through Wall Detection - Moving Target 95
8 Conclusions and Recommendations 99
A Ultra-Wideband Circuit Schematics 101
B Nyquist Theorem for Bandpass Signal 103
Bibliography lOS
Vll
3.1.1
3.1.2
3.1.3
3.1.4
Frequency Selection
Range Resolution. .
Pulse Repetition Frequency (PRF)
Image Update Rate
3.2 System Overview .....
3.3 UWB Radar Signal Modeling
3.4 Signal Processing ...... .
3.4.1 Background subtraction
3.4.2 Linear Signal Filtering .
3.4.3 Beamforming / Array Theory
4 Pulse Generator
4.1 Previous Design For The Pulse Generator
4.2 Triggering Edge of the Square Waveform
4.3 Interdigital Capacitor . . . . . . . . .
5 Multi-Channel Ultra-Wideband Receiver
5.1 Programmable Digital Delay Line
5.2 Trigger generator ........ .
5.3 Fast-Integrating Sampler Module.
5.4 Post-amplifier module.
5.5 Front-End Amplifier
6 Simulation
6.1 Effect of Signal Processing
6.2 Multiple Targets Detection
7 Results
7.1 UWB antennas
7.2 System Performance Measurements
7.2.1 Noise Measurement of the UWB Receiver
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7.2.2 Stability vs Time . . . . . . . . . . 79
7.2.3 Signal-to-Noise Ratio Measurement 82
7.3 Target Detection .............. 87
7.3.1 Maximum Range Detection For A Small (550x390 rom) Metal
Grid ............... 88
7.3.2 Target response of various objects 90
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List of Figures
2.1 Comparison between narrowband and UWB transceiver architecture [26]. 6
2.2 Plots illustrate 3 dB bandwidth of (a) an impulse signal and (b) a ban-
dlimited impulse signal. ...................... 8
2.3 Chirp signal in (a) time domain and (b) frequency domain [25]. 9
2.4 A step-frequency waveform, which consists of a group of pulses with
pulse width 'l' and spaced in T second. The frequency of the pulses is
increased linearly by A/hertz [37]. .................... 9
2.5 A experiment setup for a ground-penetrating imaging radar (GPIR) [35]. 13
2.6 (a) Xaver™ 800 by Camero, Inc. [5] and (b) Prism 200 by Cambridge
Consultants Ltd [6]. .................... 13
2.7 Mono-static radar architecture used by [57] ..
2.8 Single-channel UWB impulse radar prototype [57].
2.9 A typical experiment setup in [57].
2.10 An example of the range profile captured by the radar system (without
the RF amplifier) constructed in [57]. A small metal grid target is placed
50 cm in front of the radar. X-axis is number of range bin (spans from
15
15
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-2.33 m to 9.35 m) and y-axis is voltage(V). 17
3.1 UWB phased array system overview 21
3.2 The UWB receiver operation . . . . 23
3.3 Graphical user interface designed 24
3.4 Geometry of a linear array 28
3.5 Beam focusing operation . 29
3.6 Plot illustrate misalignment of the grating lobes in the case of UWB im-
pulse array system. . . . . . . . . . . . . . . . . . 30
4.1 Pulse generator circuit design described in [52, 30] 32
4.2 Pulse generator circuit design described in [57] .. 33
4.3 Simulated waveform at (a) node C5-RII-Q4, and (b) node RI2-Q4-C7. 33
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4.4 The output wavefonn from [57J.
Vertical scale: 500 mV/div (with 0 V offset)
Horizontal scale: 2 nsldiv ........ . . . . . . .. 34
4.5 The output wavefonn from [57] with DFT analysis beneath.
Time-domain vertical scale: 500 mV/div (with -379 mVoffset)
Time-domain horizontal scale: 50 ns
DFT vertical scale: 20 dBmldiv
DFT horizontal scale: 200 MHzIdiv (range 0 to 2 GHz, centre position
corresponds to 1 GHz) ....... .
4.6 UWB pulse generator circuit diagram ............... .
4.7 Transition time measure at the output of a single inverter . . .
4.8 Transition time measure at the output of two-parallel inverters
4.9 Interdigital capacitor geometry ..... .
4.10 Testing board for the interdigital capacitor
4.11 The circuit diagram for 821 measurement of the high pass filter
4.12 Comparing the 821 measurement for the high pass filter, using different
capacitor element. The x-axis spans from 300 KHz to 8.5 GHz. The
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38
39
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y-axis is lOdB/div. .... ............. 40
4.l3 UWB pulse generator PCB . . . . . . . . . . . . . . . . . . . . . 41
4.14 The measured wavefonn at the output of the new pulse generator
Vertical scale: 500 m V/div (with 0 V offset)
Horizontal scale: 2 nsldiv . . . . . . . . . . . . . . . . . . . . . . 41
4.15 The measured wavefonn at the output of the new pulse generator with
DFT analysis
Time-domain vertical scale: 500 mV/div (with 1.180 mVoffset)
Time-domain horizontal scale: 50 ns/div
DFT vertical scale: 20 dBmldiv (with -15 dBm offset)
DFT horizontal scale: 200 MHz/div (range 0 to 2GHz, centre position
corresponds to 1 GHz) . . . . . . . . . . . . . . . . . . . . . . . . . 42
5.1 The frequency domain channelized receiver for 0-1 GHz signals [37]. 43
5.2 The time domain channelized receiver for 0-1 GHz signals [37]. ... 44
5.3 The delay line and the fast sampler averager [30J. . . . . . . . . . . .. 45
5.4 The computer-controlled delay line and the fast sampler averager [57J. 46
5.5 Block diagram of the UWB receiver. .................. 46
5.6 The time delay generated by varicap diode circuit v.s. reverse voltage
[57]. .............................. 47
5.7 Block diagram ofthe D8 I 020 architecture [8]. .......... 48
5.8 Programmable delay line D81020-015 and D81020-050. . . . . . 48
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5.9 Microcontroller demo board and the programmable delay module. 49
5.10 Delay time v.s. programmed code for DS1020-015 [1]. 49
5.11 Delay time v.s. programmed code for DS1020-050 [1]. 50
5.12 The simplified integrating sampler operation. 51
5.13 Trigger generator circuit. . . . . . . . . . . . 51
5.14 The integrating sampler module circuit diagram. 52
5.15 Passive discharging curve. ............ 54
5.16 Integrating sampler module circuit used in simulation. 55
5.17 The simulated output waveform at (a) node R6-R8 (b) R7-R9, and V2,
using simulation circuit shown in Figure 5.16. .............. 55
5.18 The transmitted waveform that is sampled by the receiver with (a) no
reset (b) reset function, using the analog switches. The integration time is
1250 Jls. .................................. 56
5.19 The transmitted waveform that is sampled by the receiver with (a) no reset
(b) reset function, using the analog switches. The integration time is 125
Jls. ................................ 57
5.20 (a) Simplified circuit diagram (b) Block diagram of AD620 [12]. . 58
5.21 Circuit diagram for filtering RF signal [12]. 59
5.22 Gain v.s. frequency graph for AD620 [12]. 60
5.23 Circuit diagram for the post-amplifier module. 60
5.24 Graph shows (a) gain (b) noise figure over the operating frequency [15]. 61
5.25 Front-end amplifier connection circuit diagram. . ..
5.26 Front-end amplifier test board. . .......... .
5.27 Signal measured at the output of Gali-39+. A 1 GHz sinusoidal is inject
into the amplifier.
Vertical scale: 500 mV/div (with 0 V offset)
Horizontal scale: 1 ns/div ...
6.1 Simulate transmitted waveform.
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6.2 Position of the transducer elements and target. 66
6.3 Transmitted and received waveform. . . . . . . 66
6.4 The magnitude of the FFT of the (a) matched filter and (b) inverse filter. 66
6.5 The envelop of the matched filtered signal. . . . . . . 67
6.6 The envelop of the inverse filtered signal. .... . . . . . . 67
6.7 The envelop of the inverse filtered signal when Hanning window is ap-
plied. .................................... 68
x
6.8 The magnitude of the basebanded signal, after (a) matched filtering, (b)
inverse filtering with application of rect window, and (c) inverse filtering
with application of Hanning window. ................... 69
6.9 Beamformed image in the case of matched filtering and inverse filtering,
with no aperture weighting. ........................ 70
6.10 Beamformed image when Hanning aperture weighting is applied to the
Hanning-windowed, inverse filtered signal. ................ 70
6.11 Comparing the processed result with the position of the target specified
initially . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 71
7.1 Two bow-tie antennas made by [38]. Photograph reproduced from [57]. 73
7.2 (a) Sl1 and (b) S21 measurements of two bow-tie antennas facing each
other at 2 m apart. The two markers in (b) are located at 1 OHz and
20Hz.
Frequency range (x-axis): 300 kHz to 8.5 OHz
Vertical axis (a): -50 to 50 dB (10 dB/div)
Vertical axis (b): -70 to 30 dB (10 dB/div)
7.3 A Vivaldi antenna. . .......... .
7.4 (a) Sl1 and (b) S21 measurements of two Vivaldi antennas facing each
other at 2 m apart. The two markers in (b) are located at 1 OHz and
20Hz.
Frequency range (x-axis): 300 kHz to 8.5 OHz
Vertical axis (a): -60 to 40 dB (10 dB/div)
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Vertical axis (b): -60 to 40 dB (10 dB/div) . . . . . . . . . . . . . . . .. 75
7.5 The test points in the UWB receiver circuit, which are used for the noise
measurements. ............................... 76
7.6 The (a) mean and (b) standard deviation of the ADC output voltage, where
the input of the ADC module (test point 1) is connected to a 2.2 V DC
supply. ................................... 76
7.7 The (a) mean and (b) standard deviation of the ADC output voltage, where
the post-amplifier module is attached in front of the ADC, with a 2.5 V
offset added to the ADC. The inputs of the post detection amplifier (test
point 2) are connected to ground. ..................... 77
7.8 The (a) mean and (b) standard deviation of the waveform recorded at the
output of ADC. The sampler module is connected to the post-amplifier,
where the input of the sampler module (test point 3) is connected to a
50 Q resistor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 77
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7.9 The (a) mean and (b) standard deviation of the wavefonn recorded at the
output of ADC. The sampler module is connected to the post-amplifier,
where the input of the sampler module (test point 3) is connected to a
bow-tie antenna, which operates between 1-2 GHz. . . . . . . . . . . .. 78
7.10 The (a) mean and (b) standard deviation of the wavefonn recorded at the
output of ADC. The front-end amplifiers are connect to the sampler mod
ule, where the input of the front-end amplifier (test point 4) is connected
to a bow-tie antenna, which operates between 1-2 GHz.
7.11 UWB radar system with two bow-tie antennas used.
7.12 The measured voltage at the 50th sample point in the scene profile over
a period of 15 minutes. The measurement started immediately after the
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circuits are switched-on. .......................... 80
7.13 This graph shows seven profiles superimposed. The profiles were recorded
at every 3 minutes. The responses were recorded after the electronic cir-
cuits had warmed-up for 30 minutes. ................... 81
7.14 The standard deviation of the scene profile over 900 frames, which is
captured at one frame per second. The scene profiles are recorded after
the electronic circuits have been warm-up for 30 minutes . . . . . . . .. 81
7.15 The (a) (b) background profile, and (c) (d) the raw target response of a
comer reflector that is placed 1.6 m away from the radar. . . . . . . . .. 83
7.16 The reference signal, which is a target response ofa comer reflector (see
Table 7.1) that is placed at 1.6 m away from the radar. .......... 83
7.17 The results from matched filtering the background-removed target re-
sponse. ................................... 85
7.18 The results from inverse filtering the background-removed target response.
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7.19 UWB array system using four Vivaldi PCB antennas and a bow-tie an
tenna. The transmitter PCB is visible on the left side and the receiver
PCB's are visible, attached to the four Vivaldi antennas. The ADC micro-
controller and delay line PCB are not visible in this picture. ....... 88
7.20 Profile shows the (a) background and the (b) raw target response of the
small metal grid, which is positioned at 2 m away from the radar. 89
7.21 Target response of a small metal grid, which is placed at various distance
away from the target. . . . . . . . . . . . . . . . . . . . . . . . . . . .. 89
7.22 The target response of different targets. The target is located 2.2 metres
away from the radar. ............................ 90
7.23 Target response of the two metal grid targets, being the small and larger
grid reflector, spaced 15 cm apart in range. ................ 92
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7.24 The processed target response using inverse filtering with ( a) reet window
(b) Hanning window. Two targets are in the scene, placed 15 cm apart in
range. . . . . . . . . . . . . . . . . .. ......... 92
7.25 Position of the radar and the targets. . . . . . . . . . . . . . . . . . . .. 93
7.26 The processed target response of two metal grids, from all receiving chan-
nel. Inverse filtering with Hanning window is used for signal processing. 94
7.27 Fan-beam image of the scene generated using (a) simulation (b) captured
data set. The scene consists of two metal grid. Field of view = 84°. 94
7.28 (a) Picture of the brick wall (b) processed target response of the wall.
Inverse filtering with Hanning window is used to process the target re-
sponse. ................................... 95
7.29 The setup of the experiment for detecting motion through a 10.5 cm brick
wall. .................................... 96
7.30 Fan-beam images showing a person walking forward through a passage
(frames 1,2 and 3), then turning around in the middle of beam and walk-
ing back (frames 4 and 5). Field of view = 84°. .............. 97
7.31 Fan-beam images showing a person walking forward through a passage
(frames 1,2 and 3), then turning around in the middle of beam and walk-
ing back (frames 4 and 5). Background profile is not subtracted from the
raw data. Field of view = 84°. .. . . . . . . . . . . . . . .. 98
A.1 UWB transmitter circuit diagram .
A.2 UWB receiver circuit diagram . .
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B.1 Frequency domain representation of sampled bandpass signals [21].. 103
B.2 Graph showing the relationship between the Nyquist frequency and the
lowest frequency component of a bandlimited signal. Both frequency are
expressed in terms of B, which is the bandwidth of the signal [21]. . . . . 104
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List of Tables
2.1 Comparison between narrowband and UWB transceiver design. The com
parison is done under an assumption that both transceiver operated on
same centre frequency (1.5 GHz)[26]. ........ 6
2.2 Milestones in UWB system development [53, 55,37]. 11
2.3 Comparing Xaver™ 800 and Prism 200 through-wall imaging system.
[5,6]. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.4 Summary of the experiment results shown in [57]. 18
3.1 Weighting functions for sidelobe suppression [22]. 27
4.1 Comparing the performance ofBFG520WIX and BFR91 A [16, 17] 37
7.1 Metal objects used in the experiments. . . . . . . . . . . . . . . . . .. 73
7.2 Summary of the noise performance at various points in the receiver cir-
cuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 79
7.3 The SNR of the received signal when signal processing is used for the
case of the comer reflector positioned at a range of 1.6 m. ........ 87
7.4 Amplitude of the target response of different target and calculated range
for VCR) = Un (SNR=I) and VCR) = VlOun (SNR=lO). ......... 91
XIV
List of Symbols
c
f()
e,.
e fH
JL Is It fNyquist
fpRF
I1f ).
R
tbin
tPRJ
't'pulse
1'delay
l'
Zo ,
Signal bandwidth
Effective bandwidth
Instantaneous bandwidth
Speed of electromagnetic propagation within the sensing medium
Pennittivity of free space
Relative dielectric constant
Azimuth angle
Highest frequency component
Lowest frequency component
Effective sampling frequency of the receiver
Transmitted frequency
Nyquist sampling frequency
Pulse repetition frequency
Frequency step size
Wavelength
Range of interest
Maximum unambiguous range
Range Resolution
Step size of delay line
Integrating time for a range bin
Pulse repetition interval
Pulse width
Delay Time
Pulse duration
Characteristic impedance
Impulse response of the scene
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Nomenclature
ADC-Analog to digital converter.
AGe-Automatic gain control.
DAC-Digital to analog converter.
DSO-Digital storage oscilloscope.
Fractional bandwidth-A ratio between the bandwidth and centre frequency of a signal. It is defined as 2(jH-/L
/H+/L
HF-High frequency.
LF-Low frequency.
IDC-lnterdigital capacitor.
LNA-Low noise amplifier.
NDE-Non-destructive evaluation system.
PA-Power amplifier.
PLL-Phase-Iocked loop.
PRF-Pulse repetition frequency.
PRI-Pulse repetition interval.
PSD--Power spectral density.
RF-Radio frequency.
SNR-Signal-to-noise ratio. A ratio between the signal power and the variance of the
noise.
Ultra-wideband(UWB}-A term to describe a signal or a system whose fractional band
width is 2::: 0.2 or the total bandwidth is 2:::500 MHz.
uC-Micro-controller.
uP-MIcro-processor.
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Chapter 1
Introduction
1.1 Introduction to Ultra-Wideband Radar
Ultra-wide band (UWB) technology, as defined by the Federal Communication Com
mission (FCC) on February 2002, refers to signals or systems that have bandwidth ~
500 MHz or instantaneous fractional bandwidth ~ 0.20 [2]. Compared to the conven
tional narrowband radar that operates with the same centre frequency, UWB radar offers
many advantages, including high spatial resolution, for detecting closely-spaced target;
and lower probability of interception, for stealth-like military application [36].
There are many types of UWB waveform. The most obvious and simplest-to-generate
UWB waveform is the impulse or short pulse [25]. The pulse width of these impulses
is usually sub-nanosecond, which enable a range resolution of 15 cm or less, when it is
being transmitted in free space.
A UWB impulse system can be designed as such that it transmits, receives and samples
the RF signal directly. This approach eliminates the use of components such as high qual
ity oscillators, mixers and tuned circuits that are commonly used by narrowband systems
to modulate a high frequency RF carrier wave to transmit and receive information [32].
However, if the conventional receiver design is to be used, the receiver will require a high
speed sampling architecture, in order to sample large bandwidth signals [19]. Therefore,
a programmable delay line receiver design is proposed and implemented to overcome this
issue, which will be discussed in the later chapter. Consequently, the complexity and cost
of the proposed UWB system hardware is significantly reduced when compared to the
conventional narrowband system.
A UWB impulse system not only has an advantage of simple and low cost hardware de
sign, the signal itself has a wide frequency spectrum compared to the narrowband signal
with the same centre frequency. A bandlimited impulse signal (in practice, the antenna
used to transmit and receive the impulse signal tends to bandlimit the signal) with a pulse
width of 0.5 ns, has frequency components that cover from low frequency (close to DC)
to high frequency (3 dB point at approximately 20Hz). The lower spectral components
tend to penetrate through various materials more efficiently than the high spectral com
ponents. However, the higher spectral components can utilize smaller antenna designs.
Although there is a trade-off between the size of the radar system and the efficiency in
detecting target through obstructions, the overall system performance for through-wall
detection has been found satisfying. There are number of UWB impulse array systems
available commercially for through-wall imaging. These UWB array system can be used
to create an image behind a wall, which is a great tool for firefighters looking for people
trapped in a smoke-filled building ..
UWB radar was used initially in military applications [36, 53], as the range resolution
is much shorter than the length of typical military target, e.g. aircraft and missile. The
fine range resolution enhances the accuracy in locating and recognizing of the targets.
Nowadays, UWB radar can be found in many other commercial applications, such as
ground penetrating radar and medical imaging radar.
1.2 Background
The fundamental advantage of using a wide bandwidth radar is it offers fine range reso
lution, which enhances the information concerning the location and characteristics of the
target. In order to obtain high range resolution, the absolute bandwidth, which is the sig
nal bandwidth, need to be wide; whereas the fractional bandwidth, which is defined as the
absolute bandwidth divided by its centre frequency, is not necessary wide [27]. However,
when an application requires a system that operates in a relatively low centre frequency
and has wide bandwidth of several hundred MHz, a UWB system is required.
A previous MSc student from University of Cape Town, Mr. A. Chang, has built a single
channel UWB impulse radar for short-range application based on the designs found in [30,
39, 50, 51, 52]. This UWB radar system consists of radar circuitry, the data-acquisition
subsystem, the signal processing subsystem and the graphical user interface (OUI) [57].
Based on the results shown in [57], it was concluded that the system was not sensitive
enough to detect objects through brick walls, due to certain deficiencies in its circuits.
Furthermore, the system was not portable, as it used a PCI data acquisition card with
a mains powered PC. Hence, improvements on the UWB impulse system, such as the
circuit design and system integration, are necessary before forming an array system.
1.3 Objectives
The objectives of this thesis are:
2
1. Revise the existing single-channel UWB radar [57], which was constructed by a
previous MSc student from University of Cape Town. This revision is aimed at im
proving the system performance in terms of stability, portability and signal strength.
2. Use the revised circuits to build a multi-channel UWB phased array radar.
3. Design and implement an graphical-user-interface (GUI) using the Python program
ming language. This GUI should enable the user to
(a) Initiate data acquisition.
(b) Process the raw data to form a down-range profile and later, a beamformed
image.
4. Explore the potential of the system for through-wall imaging.
1.4 Limitations and scope of thesis
The scope of this thesis is to improve the existing UWB radar in terms of signal strength,
stability and portability. Hence, the original circuit design for the pulse generator and
the UWB receiver will be revised and modified. In terms of sy'stem integration, usage
of a microcontroller and construction of a user-interface are required to control the radar
system, performing operations such as initiating data acquisition.
A printed circuit board prototype of the pulse generator and the UWB receivers will be
used to formed a proof-of-principle UWB impulse array system. Experiments will be
carried out to demonstrate the performance and capability of this array system. These
experiments will be used to justify the improvements made on the circuit design, as well
as the capability of the radar system for detecting the presence and the movement of the
target.
Due to the time availability for this thesis, several aspects of this UWB phased array
system have not been investigated thoroughly or have had to be compromised. These
aspects should be considered as topics for future research:
• Designing UWB antenna for the phased array system. The broad-band antennas
used in this thesis were 'off the shelf' L-band antennas that were available in the
department at the time.
• The image update rate was limited by the serial RS-232 data transmission interface
between the microcontroller data acquisition board and the PC. The usage of a USB
interface is recommended for future work.
3
• UWB beamfonning is another extensive field of knowledge, which have not been
investigated fully in this thesis. This thesis merely noted on the differences between
the properties of conventional and UWB beamforming. There are no simlated re
sults that were generated in this thesis to prove those differences, e.g. difference in
the beampattem ofUWB and conventional narrowband phased array.
1.5 Thesis Outline
This thesis is organized into the following sections:
• Chapter 2 is a literature review on UWB technology, which briefly describes differ
ent types of UWB waveform, the historical background on UWB technology, the
UWB impulse array system and UWB applications in radar .
• Chapter 3 presents an overview of the UWB radar system. This overview includes
the design specification for this thesis, which is then followed by a discussion on
the UWB radar operation. Lastly, a discussion on the necessary signal processing
techniques required to process the received raw data is presented.
• Chapter 4 investigates the design of the pulse generator. The limitations from the
previous designs are analyzed and improvements made in this thesis, are discussed
in this chapter.
• Chapter 5 introduces the receiver circuitry required for the UWB radar. The receiver
circuit is separated into modules. A detailed analysis on the receiver circuit will be
presented in this chapter.
• Chapter 6 describes the simulation of the UWB phased array radar system.
• Chapter 7 presents and analyzes the system performance and various target detec
tion results under different testing conditions.
• Chapter 8 concludes this thesis and recommendations for future research are made.
4
Chapter 2
Literature Review
A narrowband system is defined as a system with fractional bandwidth:::; 0.01 [32]. One
of the common ways to transmit and receive infonnation in a narrowband system, is to
modulate the signal to a higher frequency by mixing the signal with a high frequency RF
carrier signal [32]. Since a narrowband system only operates within a specific frequency
band, a large number of narrowband systems, which operate at different frequency bands,
can co-exist in a common environment without interfering with each other. Hence, most
conventional radars are bandlimited narrowband systems.
Ultra-wideband (UWB) technology, as defined by the Federal Communications Commis
sion (FCC), refers to signals or systems that have bandwidth 2:: 500 MHz or instantaneous
fractional bandwidth 2:: 0.20 [2]. Compared to the narrowband radar that operates with
the same centre frequency, UWB radar offers finer range resolution. For example, a nar
rowband system, centred on 1.5 GHz, that has a bandwidth of 15 MHz (equivalent to a
fractional bandwidth of 0.01 ) has a range resolution of 10m; whereas a UWB system, also
centred on 1.5 GHz, that has a bandwidth of 300 MHz (equivalent to a fractional band
width of 0.2) has a range resolution of 0.50 m. With finer range resolution, UWB system
is able to reduce the amount of clutter within the resolution cell, resolve closely-spaced
targets in range, and provide high-resolution range profile, which enhances in locating
and classifying the targets [37].
Figure 2.1 shows a comparison between a typical narrowband and a UWB impulse transceiver
architecture and Table 2.1 compares each module of both transceivers in detail [26].
A UWB impulse system directly transmits, receives and processes the RF signal, which
eliminates the usage of components such as high quality oscillators and tuned circuits.
This significantly reduces the complexity and cost of the system hardware. However,
UWB receivers require a more complex sampling architecture, as a high sampling rate is required for sampling large bandwidth signals [19].
5
,..
, . -. " ..... ,
,-...... ,
L "" •• ",IIcI> •• ,d
[.u.xI plft '<>fIO"'"" .. ca.il) Cot....: ....... rn_ '. ~l!!l< .. ~ h' j ... ~ ... ,~bIt ~ .... lJo< ~,... «h,,,, ,,,, •• 'hI ,~r. .. m¥
_________ ..... "''''.d'''·'--_______ S-:::;:-''' " • ~n<r. .. ,,,,, fl' ·tv'" < If" otl.hoNl
l non. ..... < .. H>tr·'~-<'-..bo1l l" ..... po"""'" .....,""fl~ .. ,J
... "",,'bond IN'I .. ~ "";' '" R.II.h C _________ --,,,==,,==::::-:::c;;;-___ r'u=',d ~~ "'./I"~
Rt<ju, .... III ... " .... ,,,d ~ I '" nn:J
.,..JllA.o . :;:::;-;:,,:c-'---------------, 1I,~b r~ •• n<' "",,"':;"t.a.oJ ....... 1
I> 31'1>.'" """" • ...., In. '"~ .. ,
1=[' <0<"\ , -. trun .. hlllnl/. be[.""
." . do~~ottd IIme<".'''''
... m,..~ ~'n ""I~ ""1""" .\ DC ,, ~h ,......,..,... =-..1"'lOn on.!
II"'"" ..... ,.1"" e'l h,!'h "'r""""~" A IX " '" U 'Rl' I1nr ,,,' h 0""".""1 .. ",<1,<"<.<,,,",
---------+,-2::;;"~'" N""",""ha",,, oIco<c'i .... !In trn> .. ~r - C ,,1>::''''1 <kt\.,,~", ... no p"" .... u_ ,01.";,,,,-," ... ,,,,,,,~ , '''''' ft-I.",ntc< .. ,-"q,,,,cd
T.bk 1 I Comr:m""", bct",.= ""m~ 1I,,,,d lind UWH trnn",~ ,,"er de.>ign. The c"ml"'ln . ...... , IS d.~:>e under :on ~lImpuo:l tllat bOIl! transcc) "cr "p .. ,,,,,,-<1 l'n ""m~ centre' frc'Iuen,-y
11.5Gl lzLi26l-
Anmn.:r ~~~' RCI\ dliinge of a I, WH ,)'SINn,s IhBt II " lIer, )""'Tf pi I}b~bjhty of itllcrcql
t ILln , UWIl ~ 1~ lIal ~ ha'·e n I",,'ct 1'::; II (l>(lwCl' 'I'ttt r~ 1 density J tlla" a Ill1tTQwband systcm
rodmnllil the snme ~vcragc I,,'''cr, Tn..: PSD [)f R L ""8 ~1J.:,,~llooks li ke: \h~\ OfGHUUlatI
d' llI111l1l~'d nUISC to mu'\ IIflfrQ"oonJ d t1C~'hQn sys!t::ITl$ [.17. 431.
nil: n:sl III' lh, s . 1I ,l,II\:r will pn:mu a literature n:,icv.' on UWU systcm~, lndudmg an
IIU" • ..J"",llon t" ~hlrtrcm I>JleI of UW U wa,dorm and ~ brief dc-s...riplion on t/'.c pas! work
on L'WB impulst' r;I(br sYSI~m A dl~u"'~lon on lhe UW H Impul.'" array <~,tc", will he
plt"s.cn:, wh i. 1I is lhen follo",~d by H~ apphcations m I h~ mdustry. 1. ... , 11 ),. ~n aM I ~,,~ ''''
11K- s)~lcm pcrlom\3l\cc of ~ Cn\lIng "gnal .;.;han,d IJWH radar at the L:mwr.lt) ur
elp..' To" n .. ,11 "" Pf'I:!;Clll
LV. H ..... ~vcf"""s ';In he d,\'odNi mill three malll c.:tkg(,ries: Impulse. hl\C!IJ" frcquen,·y
moou l311011 aml llcp-freqllrocy wavefonn ,\ ithr.ugh lit:: dfcclI\-e hllJldwtdl h ,~ :l..h,,,, L'd
dlfferenlly ""nh d ,ffcrcnllypc "f "'-:I,·dorm. the :,t"ge n:sc.lutKln loR. fm all th,ce .alc_
g(lf)Cs (~g(\~n hy
" h~l~ H, r, " lhe eft; .. "t II\: b~nd" Kllh ant! (' IS the ,pc.:d of clecln,lI11l1g:1d:.- IU"Up~gall<lf1
""ll"" l h~ ,('11$1111( mW'lIm [3~ J.
2.1. 1 Impulsl' lSlwl"1 I'ul ~ ,,)
A" I ml'ul~ ~ (g!\al. "1!I~h '" a puis.: ",Ih pliise ..... ilht. lyp lall~ k:S$ than I n, [ZS]. ~,
~hv"n ill "'GUOI,: 2 2(a). I,a., a 3 dB bar.dwld\h B oj"
, R ~-
1,
'" he.e T " Ihe pul ,~ durn( ion How,'w,. UI PfllC\'''~, III,' anl~nn:o usc'll til trJII .1Il1l ~11o.1
1 a;~ ,,"C Itoe '"'rul,,' Mg<\» II~' ..J~ tl} h31K1 li m,1 1m, .,g~ a\ H"l1CC. lh,' 3 o.ID b»nolwi o.!\ h H QC
a "ar.,IJimJtcd nnpl.ll,e "lltn~l. II>' ,00...." i" F,!:Ulc Z.2(I>). I~ dclcrmm"ol h~
, II '" -,
.40 bandhmllcd sub· nl\llCOSCcoOO Impuhc ha5 spectrum tvrnponc ntS from clllSe to IX 10
>c,·tnl GHl H,·n.:.:. larg~ dli,.:liw banJ",o.Ilh. " 'h,o:h ,mph!;'! higb nm);c r~ohlliun, C3D
"" a.h"",.-,j '" Ilh a ~lIlgl~ 'mpul<e
T --..
t \
(a)
(b)
!\ (\ I I \ f\B~:; I I \ ; , \
) I \
Figure 2.2: Plots illustrate 3 dB bandwidth of (a) an impulse signal and (b) a bandlimited impulse signal.
Another advantage of using an impulse signal is that it provides an accurate time delay
estimate between the target and the radar system. This is done by measuring the time
elapsed between transmitted and received signal. This time delay is dependent on the
range of the target [19], i.e. 2R
'Cdelay c
where R is the distance between the target and the radar system.
The hardware design of an impulse generator is relatively simple and low cost if only
a moderate signal power is required. However, the pulse energy is relatively low as the
pulse length of an impulse is very short, i.e. typically sub-nanosecond. This sets a lim
itation on the system performance in terms of maximum range for detection, especially
when it is used to detect a human target.
Another issue with using impulse waveform is that an analog-to-digital converter with
a high sampling rate is required for digitizing the received impulse echo, if the conven
tional receiver design is to use. High bandwidth and high resolution ADCs are expensive.
Hence, researches have been conducted to investigate suitable low cost design for UWB
impulse receiver [51, 52].
2.1.2 Chirp (Linear Frequency Modulation)
The linear frequency modulated, or linear FM chirp, is widely used in high-resolution
radar applications [25, 37]. A linear FM chirp waveform is a sine wave in which the fre-
8
quency increases or decreases with time. Figure 2.3 shows the time and frequency domain
of a 100-400 MHz chirp with a chirp length of 1 Jl s.
T lime c
(a) Time (left) and time-frequency (right) domain
(b) Frequency domain of a 100-400 MHz chirp signal
Figure 2.3: Chirp signal in (a) time domain and (b) frequency domain [25].
A chirp waveform attaines large bandwidth by increasing its frequency with time, instead
of by decreasing its signal length. This has an advantage of increase the signal energy
while maintaining the high resolution ofa radar [25].
2.1.3 Step-Frequency Waveform
A step-frequency waveform is a sequence of coherent pulses whose frequencies are in
creased from pulse to pulse by a fixed frequency increment!1f [37]. Figure 2.4 illustrates
a step-frequency waveform.
fo+2l/ o /o+(n-1)4'
»>-....... 0---'--
Figure 2.4: A step-frequency waveform, which consists of a group of pulses with pulse width T and spaced in T second. The frequency of the pulses is increased linearly by!1f hertz [37].
The pulses in a step-frequency waveform have same pulse width. Pulses used to construct
step-frequency signal is typically narrow in bandwidth. Hence, narrowband equipment
9
(except for the antenna and transmitter) can be used to implement step-frequency radar
[37].
As mentioned at the start of this section, the range resolution is determined by the effective
bandwidth of the waveform. The effective bandwidth of a step-frequency waveform is
given by
Bejj=NAI
where N is the number of pulses in the waveform. Hence, large effective bandwidth can
be achieved by increasing the number of pulses in the waveform.
Since each pulse situated in a different band of frequency spectrum, the radar receiving
echoes are usually recorded separately for the different bands. The recorded data is then
combined and reconstructed to form a larger portion of the scene spectrum. However, if
not designed properly, i.e. Binstant < AI, where Binstanl is the instantaneous bandwidth of
the step-frequency signal, the processed data will contain gaps in the spectrum, and possi
bly yielding ghosting artifacts [56]. Hence, researches have been conducted to investigate
methods to process step-frequency waveforms to reduce these artifacts [23].
2.2 Past Work in UWB Impulse Radar
UWB technology can be dated back into the late 1800s, as Hertz generated a short elec
tromagnetic pulse using a spark-gap generator [24]. Later in 1901, Guglielmo Marconi
developed the first spark-gap radio, which he used it to transmit Morse code sequences
[32]. However, at the beginning of 1900s, the idea ofa large number of radio links, where
each operate at a specific frequency, sharing a frequency spectrum, become popular in
the communication and radar industry. Hence, narrowband systems were widely adopted
[37]. By 1924, spark-gap radios were forbidden in most applications due to their unregu
lated RF emissions that were disruptive to narrow-band radios [19].
However, the low signal bandwidth limits the ability in radar applications to detect closely
spaced targets. Hence in 1960s, UWB impulse systems were revived, with the pioneering
contribution of Harmuth, from Catholic University of America, who did much of the im
portant early theoretical work in non-sinusoidal impulse technology; Ross and Robbins,
from Sperry Rand Corporation; Paul van Etten, from the US Air Force's (USAF) Rome
Air Development Center; and Russian investigators [37, 53, 54].
These pioneers investigated the UWB applications in communication and radar, and the
basic design for UWB impulse system, including the transmitter, receiver and antennas,
were developed [53]. Table 2.2 summarizes the major milestones in UWB impulse system
10
development after early 1960s.
Year I Milestone
Late 1960s The development of commercial sample and hold receiver (Tektronix
Inc.). This receiver architecture uses a sampling circuit with a short
term integrator. This approach enables UWB signal averaging, which
lower the requirement of the receiver's sampling rate for a UWB signal.
1974 UWB ground penetrating radar (GPR) system is developed by Morey, which is commercialized Geophysical Survey Systems, Inc. (GSSI)
Early 1970s The development in avalanche transistor & tunnel diode detector
1994 T.E. McEwan, at Lawrence Livermore National Laboratory (LLNL),
invented the Micropower Impulse Radar (MIR). This is the first UWB radar to operate on microwatts power, and the system offers extremely
sensitive signal detection. This technology have been licensed for
various commercial applications. The MlR devices are estimated to cost
about $10 in sufficient production quantities.
Table 2.2: Milestones in UWB system development [53, 55, 37].
2.3 Ultra-Wideband Impulse Array System
A single channel UWB impulse radar can offer high-resolution range profile and resolve
closely-spaced targets in range. However, it does not provide angular information of the
target location. In order to obtain an image of the scene, an array system is required. In
addition of using an array system, the signal-to-noise ratio (SNR) of an impulse system
can be increased. A N-element array system can increase the SNR of a single-element
system by N factor.
A UWB impulse array system for 2-D imaging, usually consist of a pulse transmitter and
N elements of receiver. A UWB array system has several advantages over a narrowband
array system, such as high range resolution, grating lobe cancellation, permitting the de
sign of sparse array and inter-element coupling reduction [40].
In conventional narrowband array system, the inter-element spacing is constrained to be
less than half of wavelength to avoid spatial aliasing, i.e. grating lobe effect (refer to Sec
tion 3.4.3). This creates a practical limit in the size of the antenna aperture of conventional
phased arrays. The size of the aperture affects the angular resolution of the array. Hence, high angular resolution narrowband phased array system usually consists of large number
of array elements, which is not a cost-effective solution for some application. Furthermore, as the inter-element spacing decreases, the inter-element coupling effect increases
[ 41]. The effect of coupling consists of distortion in the main part of the direct signal or,
more often, in the addition of extra-ringing in the signal tail [41].
11
Rc~an:hm; [JJ. 45) bl~c >h1l"'11 UUIl gnWlr. lows an" ~ppr"",sN in r.;WD Irr.pulsc 31
Ill} bC'3mformmg. A Onef nplimauon and iUu.~lT3lton IS PICS<.1I10:-0 in s«.iOll 3.-1.3. Thl~
Wl'qUC propcny ofUWEl lClplllsc amI\' allows sparse ~m.\ dc!.lg:I and lK'hlC'."ts hl~h an·
gular =lulJon .... Ith only 3 fe .... arr:t}' elements
I" trrm~ ,,' Imer .. demcnl cocpl lnr .. ,1U(I,a; [40. 41] have o;hn"',, .h31.he cnuP"1Ii pile ..
norrn:n.i III lJWB ..".ay~ .. lali ~ft"ClOVC than In :be ,:1..'1(: Of nltfTnwhlnd ltITlIy~. alld Ih~
phen~'I1le"., ,~nq:J'r ,hie" nero th" L W R lOI1"ay, are ct>n!tgure<! ,n 01 <pa= arnl~ 'ilrrtlltll"n
lI.~emly. UWB ""pu! .... '"!> arra~ ~~sl< . .,n. baH been propro!o<"d tnr 1Il1Lll> aflplic~lIiln<. In ..
.;luJm~ communioal ,om, • ... dar. rem01e sen." ll.\: ;o.nd ond, ...... " Jl("I!'iuoll inll [41) J
2 .. 4 Applications of UWR Impulsi..' Arr:I~' in Ibdar
In rt<:en. yean. eWB 11Id.:trs h!fl'~ becom~ vcry popul1tJ for miliUl<) ami ml~.hc.llpplteft·
lOon. UWU m:.puJsc systoms art" mamly u\-ed for ~,on"I1illl:~ I~'¥~I loc~un!l :,m.llm'~m!l
apl'hcluons Vehic k collision· 3voida .... xc I3dllT ii I "ell know .. ClHTlmm:IIJ L 'we ttn ¥et localtnll sys.em [34. 4']. Th= = many imagiDl: ~ysk"ms mal lISe UW8 'mpul,c lreh ..
nolng~ Two IYllC.~ of l:WU ImlIglOg Ipplications mSI "itllx JI5CO~' In mI • .;:elton 1ft
''''n...:k'~uuclt~e evalu.:mon sy!>lttnli and thrnu~h ...... allimagtng sys.tnu.
204. 1 ~on-I)H'lrurlivr [\'!lItt:Jl ioll
'1 .... 'I.ce-II\I<..'I' le (~I IUJ!lon It.:Df\ IO)Ynns lIlT used to C\"3IU31~ tb~ cooouion and mt"
p ..... 'J!<'rt}' nf I m':llmll .. wr:h as "ails. ro~c:s and bridr.c d«k.< [n) .. TIll: ability LO de ..
Lt<:1 L-.d .... ;.No~ the cooouion of;.b~ SUUC<Wl" IS 'm!'l'J1an' tu d~"Jc .. h"h ....... TI."-plll! ('r
to ",,,Ixe tlx CUrI\"TI! SlIOCIun: GlU\ffid penrn .... inl: ni<b.r t~ 01 r ... nn ... r ~OE. F '@Uf( 2 ~
UtOll"S an I"lIpoI.'11mcD1 ~Ct Up r.". • )II\'u"" pcnCU:OLIHl: in,a~lII); I1iJar (G PIli. ). whoch is Jt" ..
Hk,pto.I by l.",mcc l '''TtIl<.">rC ~~!i(rna l l..aboral",} us.-d 10 C\'ah. ... le the !-Iru::IU,'" nf
bnd~~d«hP5J
hl!ule 2.< J\o"'~ a VWH ImflU1.sc r:tdar system. "hlc~ i5 mounlo:-O nn top of J les~ bed
Ih: leSt bed I~ made of I CDocmc sbb \hili ,onUlin~ reonror;;ml! bars By ml."'inl!t tbe
r~ S}'\lt'm OVtt Ihe lUI I:w:d. il ~,mul~I~~ the ml.'tooll ..,f ~n ",~pe"l1"''' 'chid~. II illl a
fu..:d "new array of ~CC'~IDII: :UU~nnB~ "Wr a bridge ded. [35 J.
Th .. • ~'.lcm u.C\J "cl"""~o'~r)' .t,(\(Ie~ I(J g~nc:rJlc t~ L'WB pulr.e . This pulse generator
can ~cm11l'c PIll,to. w'lh [lI.';l ~ fK1"e. at In.;;''' of I 00 v. , wuh put,e W,dLh of I 00 !Il .100 p~.
The h .. ",!",dth nfthl~ sillnalis approx lmaldy II (1Hz. rhe pulse repelIlion frequency II
sel Yp to S .'1Hz..
2.4.2 Through-Wall hll.a~in~
Throosh·"DIl lIuaglng ~y~lcnL' an: a n:bm dy nr." applI<;311,," fur UWB l~hn"lng).
The>' ClI"l Ix us:d to nbsen e lhe IDyO\lI and m<>1 iOll "",ric;,. oollrllllg Thmugb-"all ''''''1:i " ~ can he ustd by poliee Mrl fitdighler' In locale lhe people il"",," _ boulll'ns. m lhe ~"'"c
or I nosugc ~riS)~ 01 a fire :.::cidcm [:.''I J.
T"y comrnrreially avaIlable (I!rougl!-wall Imagm~ syslem are t .... md. ~all1e1y X~'·eo·r'-1
sy~~cm ">' Camcro. Inc. In Sllol>.l1 m F,!Yre 2.()(J). and I'TI~ln 21111 ": Camhri,lgc COl1-
sul1.m~ LId [bJ. slmWJl In rl~re 1.6(h\ Both s,'slems can .,eo IhmuSh "'():<;~ com",,)nly
u.t."d ".11 m;rKTlals. loch lIS bnck. COIIcre1C. 1'100<1 and Slone. Tahle 2.l cnmrar<"S thc~~
I"U ,V!>lems In lennI of phYSICal structure and the 1)'Slem rll!:';lgn.
fIgure 2.6: (11 Xa,·crn.! 110(1 by 1..3lnem. hlC (~I alkl (hi PI"m ~{Ml 11:0' ("~m1:>nr.l~r ("un,ul\anl~ Ltd [61.
1 ..... ",_ !-,h~I:n>k",.I ",~ ) -diu","l>I<ln.1
....... .. ,1II1l ~01""'''''' 1'''1!'' 10,,1 r", : -dim."",(Jc,,1 '''''\II'''' .,,,1 ~ m I", '-<tj",.'n"""'I'm'£ln~
'IItlj1:hl 11 • ill'n,I,,,lln, bIomm<_< I Si.. Mem, X~,m· Hem
P"'"'tI' (, I I\ """"I~"'"~ "'"<nO' (! 1 Malll> P""''''' ""'R~
(,tId(lf,1t\< J "' .... ,nN><h .:1lmU'h""d <~·""'"
~)""'m rRl' _ N..~ """"(,,,L
I Frrqu"" O) !'OIl~< lG11l \u 100H" RIIo,_u<""I"";)n Lo, a,,,,.i! !lfI.
"""'" 100
~-~"JI"""".al ond l~ ...... ~
~O'" _J \' <, I'r>d\Od,nc l\ulnyl
~'"'" ~ 1(1"" ' H"",
I ""~ ... ~' rad.
,: it' In ... ",,,"" on<! ~ ..
:fcv.w<.lO.
)0011>
!1 Gfb ""~,' GItt. ~o< ..
2.5 Existing Signal-Chan ncl U\VB radar at University of
Cape Town
A prt'''iou.~ ;'ISc SNdenl fmm Uru'en-II), of CIIpC T, .... -n_ \It. A Chang • • b,gnc<' And
blUh a Sl ng!e·dwU1C1 U\~ D 1I11f'ul<e f1Ml., fur ~b"I1 'IlII\!(C' ;,pplU:iIIIWl nilS L~'B r.l<l",
system fonsiSI5 tor noJsr ~1rt'''Ht). :be IIl1u.· • ..,jU1MIJ'm ."h~)-~tcm. Ihe MJ!11l11 V' ",-",!;"g
sul>sy;tem &lid the ~tlIl'lI"'1I1 U</:, In,crface In].
1'1111 of I II ,~ 11k~,>'~ _>t>jccu'e b It' ' ..... I>C and l!!enuf)' the Ilehei<:nc i..,. m lhL< ~~,;t,",," and
OO"-~. tmp'"'''''' Ih ... S~'>,enl I"-Trvrm.'k"" The dCl l' le. l lltIa l~~" ,.,.., t~ "'U1seel\~r c ,r.;:u"
do;.s')m. I.' Ihc puhe g~"c,a'or and t WH ,cce. '·~r. "Ill be pJ\.'SCnloo m Ch.lrl~r ~ and
t:hapter.o; ~h'~}' The m:un I"e~ nllhls ~Cl1011 IS 1<J an:l\yze Ih~ sy51~m perfor·
mlLrtc, r ... III" slOJ;k·chaHl'ct I, \\H I~"" ~>(':m. tlgutC 2.7 sho\l.'s the syslem layoul
;on(! FII:UfC : k show$.llIe r.ld;o.r CIrcUli ~rd of Ihl! radar ~yslem
Uunng tbe radar orerauOll. th.: pulse Ilcncrawr ' ~tnlljl;c'T\"d by Ihe "I"...-e """'C. " h"'h ,~
generated lIy the pulse 1I111 n ~rnl"",lol nl~ rc,'C I"lnl! >lgn~! IS 1i<t11lpkd I>y lhe r,,,,-;am·
pl ~r. It> ~"""n III F,~,,", 2 7, The la,1 >IImplcl 's l ro~@ered hy the ddl~",l l'll~~. "h)~h
I, grnlntll-.l h}' 111~ pul"" ",,,n cellCfa1<" and p .. ~.ed lhm ugh I &Ia} lonc. The ddl) IS
<ct II)' lit<: dela~ tm~ . '" h'ch eoch UI11i; dc:l1)' COtr~Sl"X'ndS 10 a panlcular nl:ll1-" !Tom tbc
" .dar rh~ delay , 0; let Irl ~ Wl(:h:L"lged fOT 3 numbt"r of pulses. ,hcrdoo-c Ih~ sarr.rlcr will
wnrlc lbe rerum c.::ho 81 a nlnC dela>' for a number of ume. An .mcl-'flIltor IS u$C<llo
lmcgrolc the !oampled echo. fly tncrt'nUllllhc lIelay time llencr~h;.J lIy lilt Jd~y lim,. n I'
dfccllwly samphng the rc.::c" '"~ s'l:n~1 "I "ari"u! IlInll'" fwm ,hie r....!ar Hl"TK'e . ~ ,~nl!c
p .... ,fik ","n l!c Ohl~illcd
-
,.,,,,~ .. ,,, ",,~ .. ,""' ..
. ~ --
I ~ ••
> .~ -
, ,
• T~ me~5um;l pnk \'oh~ll~ofthc transmmed pul<;,: '" 1.2 \"
• TIle calc"l~letl p'~~ bandw,d,l> <:- lJ I 7 MHz ( .... LlllO,,1 apph""I'O)O uf Hlinn illl!
.... '0100 .... )
• The cak~\~lro T1lI1se n"'SOIUliOIl J$ oR ""' 0 16 m.
hpcnm~m5 .... ·crt" Cftml-d OUI USIIlS ""'0 bow-tie anrcnII:JS. wl>lch opel1ltc be1w~n I G Hz
and ~ GHl. (jnd rc ~ cnoT$ and ~ metal ball wen: used is ulrgm. 1\ tYJIinl experimen:al
setUP 1<1110"'0 In rt,ur~ 2.9.
1\ !'jallonJIIMtnJrncnl OKt. Acqu"lIIun (NI-DAQ) CIltd CI'CI·60'OE),~ usc.-d to pr"'tdc
ilIl immltCc Ixtwc~""O 11K' "umpute, IOI1d 11K" nod:lr Clr~ u'l 151l A Acr lloc IJOdar L",:u,1 ... m
pk~ 100 '~Tl:el n· ' llUn<c. Ille [lAQ ~1It<1 I) U"'..! III d'glt,ze 11K: r.:c.;" <XI \' j;Il.1. and lnlll"""\
It bllC~ to rile comp uter. ".~ Sri'loiLll rmceSSlrle IS performed. I"h~ i)AQ card rro\HI~ III
lmubplexed) I ~-hlb ;>..IX · channel>. ""ull ITUU.lmum samphng r.ue of L 2~ \1~ s (mega •
.... n'ple.per·sccolld\. Thl ~ DAQ.-wI U5C"S lhc I'CI bus. 1 e. n ffiluiTC"~ I;) lined onlO Ille
motllerboard dlrt-nl,. Therefore. 11m s~'<tt-m i~ difficult w ~ tamro around
• 1\: .<IM! 0 1 e"",11 nperrment. II Ix>.'l,rrMlnd lIrn1ilc" i~ CJl'luft"d Til l' hackJm""d
rrrolile N nt:uns «hcw:~ from the $Il1tronat)- obj(".:tS In 1M s..~cw: . sucb lS tabl~ 3I1d
chalU
• Aft~r 1M bxkground profile has h«n tlIl;tn. l:II1ln~ are pla..--ed to the J..~IIC" Another
d;)'\l1-rDnr~ prohlt IS captur-e-d
• The !>Ccond caf'lurcd rrofile .. xmtain~ the cdw fmm the target. a> wel l a~ th~ e<':h<>c~
from Ihe ,taliona,), ohje.':t, III the >Cen .. Hence, Ihe haelground proli le IMI ",m
~apluro.l earli...,-, ~an be ,,-.cd 1<J rcIHU' e the back~ruUJHI "h'l1er from the laler PfOft1C.
(0 '<:'I'cal the true :It1}(et n;~ron'c.
• The hao:.'k l:fuul1d·r~mo\"cd target rCl>punbc I~ PN<''''"e.t ,,,Ih ~n in' en.<: liller, dc1ined
between \ GH~ and 1 GH~ A Hannm~ wind,,,, IS appl ied to ",d\lCClhc snle-lubes
"fth" IHt...,-,"<I signal.
Figure ~ . 1 () <;hm, <; n ran8~ pn)ri l~ ohtalncrl u<; '"/! Ih i~ ~in8Ic-channd UW B radar", ,thrJm
ils front_end amplifier, In" targ~t. a smail metal grid (dimcn,iQn. 5~O~W() mm). i~ pln .. .."d
50 em In front Oflhe radar ~'gUfC~ , III <ho"'~ thai th~ recc lved and ""mpled vo ltage of a
,,,,all "'/:Tal gr id wrget IS apprO~Hnaldy 'I" mV
00 ' -~~--------__ _
j
i : ))1 ' I
Figure 2.10: An nample oflh~ ra.ng" rrofi le captured hy the radm ,;plc", (wllh..,..,t the Rf amplilkr) comtructro in [5i[. A small ml:lal grid target i~ plaud 50 em m fmm <If t~c ,.d ... X·a,~i~ i. numlx--r orJ3n~c bin (SP3n.1 rrom -2.33 m 10 9.3~ ml IIIId y·;L~lS IS \,<lhRS::(V)
l ahle ~"summarm::s thc re,,,l!> oblained flUm l~7[ .
17
Experiment Experiment setup System gain Results setting
Maximum A small grid reflector (1) Without RF (1) In the target response profile,
range (550mm x 390mm) is used as the front-end the target is visible up to a range of
detection target. The target is slowly moved amplifier. 1 m.
away from the radar. At each (1) With RF (2) In the target response profile,
position, a target response profile is front-end the target is visible up to a range of
captured. amplifier 5m.
Detecting 1\\'0 targets were used: a metal ball, WithRF Two target can be resolved from the
multiple which is placed at 1 m away from front-end target response profile.
targets the radar, and the small grid amplifier reflector, which is placed at 2.5 m
away from the radar.
Detection • A wooden partition with WithRF • Target detections were performed through dimensions front-end from 1 m (the distance between the
wooden 120(W) x 2(B) x 180(H) cm is amplifier target and the radar) up to 3 m. At placed at 1 m away from the radar. 3 m, the peak voltage of the return
partition • A small grid reflector echo {after background profile has
(550mm x 390mm) is used as the been removed) is 0.338 V. The gain of the front-end amplifier used is
target. The target is slowly moved :::::25 dB. However, the gain of the away from the radar. At each post-amplifier is unknown. position, a target response profile is • Comparing to the target response captured. of a small grid reflector positioned
at 3m (without obstructed by wooden partition), approximately
20.5% of signal voltage is attenuated by wooden partition.
Detection • The radar system is placed against WithRF Target is only visible when the
through a 23 cm thick cement wall. front-end target is placed next to the 23 cm
concrete • A large grid reflector amplifier thick cement wall.
partition (830mm x 485mm) is used as the target. The target is slowly moved away from the radar. At each position, a target response profile is
captured.
Signal-to- .10 noise profiles are captured and WithRF • The averaged noise profile has a Noise (SNR) averaged. The noise profile is front-end peak value of 4.28 J.LV.
Ratio captured without target in the scene. amplifier • As the target moved away from • A unspecified target is placed in the radar, the peak value of the the scene after the noise profiles return echo dropped from 3.28 mV have been taken. The target is to 0.425 mY, with target moved slowly moved away from the radar. from 1 m to 3 m. The SNR is At each position, a target response reduced from 57.7 dB to 39.9 dB profile is captured. respectively.
Table 2.4: Summary of the experiment results shown in [57].
18
Chapter 3
Ultra-wideband System Overview
In this chapter, the UWB phased array system architecture will be presented. Firstly, the
design specifications of the UWB system will be introduced, which is then followed by
a brief explanation on the radar operation. The signal processing techniques that will be
used in processing the raw data will be discussed the last.
3.1 Design Specifications
3.1.1 Frequency Selection
As discussed in Section 2.1.1, the bandwidth of a bandpass-type (i.e. spectrum similar to
Figure 2.2(b)) is determined by
B~ l/T
where B is the 3 dB bandwidth of the pulse and T is the 3 dB pulse width.
A bandlimited impulse with pulse width T r:::; 0.5 ns has a bandwidth of 2 GHz, which
has significant frequency components from very low frequency (close to DC) to approxi
mately 2 GHz.
In order to perform through-wall imaging effectively, the system frequency selection is
important. Although the low frequency components (below 1 GHz) have better penetra
tion through solid material than the high frequency components, antennas which operate
at low frequency tend to have a large structure. Hence, one is required to select a fre
quency spectrum, which has moderately low frequency, for good material penetration,
and still works efficiently with moderately small structure antennas.
Hence, this UWB system is designed to operate between 1 GHz to 2 GHz. With 2 GHz
being the highest frequency component, the minimum sampling frequency required is
4 GHz according to the standard Nyquist theorem. If however the signal is bandlimited
19
to occupy a range between 1 GHz and 2 GHz prior to sampling, according to the Nyquist
theorem for bandlimited signal (refer to Appendix B), it is actually possible to sample
at twice the bandwidth in this case, i.e. at a rate of 2 GHz. To retain flexibility, it was
decided to design the system with an effective sample rate of at least 4 GHz.
3.1.2 Range Resolution
The range resolution, tlR, is measured between the 3 dB points or half power width of
the point target response in the range direction [22]. This also indicates the shortest
distance between two adjacent targets at which the radar system can distinguish the targets
separately. The range resolution is related to the bandwidth by [22]
c tlR';I:j 2B
where c is the speed of electromagnetic propagation within a sensing medium and B is
the bandwidth of the transmitted pulse.
One of this project's intention is to detect the presence and movement of a person behind
a wall. It was noted that a person's dimension is normally greater than 15 cm, and under
normal circumstance, people tend to stand at least half a metre or more apart, to avoid
feeling uncomfortable. Furthermore, a step-size of an adult is usually greater than 15 cm.
Hence, it is concluded that a range resolution of 15 cm should be adequate to detect
human presence and movement. This sets the required process bandwidth for this this
UWB system, which is 1 GHz.
3.1.3 Pulse Repetition Frequency (PRF)
The pulse repetition frequency is defined as number of pulses transmitted per second.
Consider a radar system transmitting pulses at a frequency fpRF. The time interval be
tween the two successive pulses is known as pulse repetition interval (PRI), which is
given by tpRI = 1/ !PRF. If the total time taken by the transmitted pulse to reach the target,
and return to the receiver, is longer than IPR], one cannot distinguish whether the echo is
return from the first transmitted pulse or the second transmitted pulse. Hence, in order to
accurately determine the range of the target, the pulse must be transmitted and the echo
must be received before the next pulse is transmitted. The PRF determines the maximum
unambiguous range, R _ clpRI _ c
max - -2- - 2fpRF
The PRF of this UWB system is set to 2.5 MHz, which allows a maximum range of
Rmax = 60 m. This maximum range is well adequate for an indoor application (allowing
for multiple echoes to die down). Since the room used in experiment is approximately
20
5 m long (across the room), the maximum range for the sampled down-range profile was
set to 5 m.
3.1.4 Image Update Rate
In order to keep the through wall image update as in real-time, a sweep rate of 10 frames
per second is desired. The maximum sample spacing, according to Nyquist theorem, is
2c!H} = 212:\0;9) = 0.075m, as the system is operating in the range of 1 to 2 GHz. Since
there are 4 channel receivers used in this system, the total number of samples per second
is sam;r::pace x 4 -7- 0.1 = 2667 sample/sec. This is equivalent to the maximum allowed
time that one can spend integrating for a range bin (refer to Section 3.2) tbin = 1/2667 = 0.375ms. For a PRF of 2.5 MHz (PRJ = OA,us), the maximum number of integrated
samples for each range bin is !..bin.. = 0.375ms = 9375. This ob1ective will be reviewed in tPRl 0.4 us J
Chapter 5.
3.2 System Overview
D RS232
ADC Channels
Transmitter Pulse Train
.-~SI=id~in~R~a~n~e~G~~~e __ ~[ Digital Delay Line
Instrumentation Amplifier
Fast Integrating ..-/1 T Receiver 1 Sampler ~
RF From-End Amplifier
Receiver 2
<J--I R"",,~ N
RF From-End Amplifier
Figure 3.1: UWB phased array system overview
Figure 3.1 shows the UWB array system block diagram. The UWB array system con
sists of a single transmitter and multiple receivers. A microcontroller, PIC18F4523 from
Microchip Technology Inc., is used as a centre piece of this design. It was chosen to
21
provide various controls and portability to the UWB array system. The functions of the
PICl8F4523 are briefly listed below:
• It generates a square wave train, using the timer and the pulse width modulation
(PWM) modules 1. The square wave is used to drive the transmitter and receiver.
• It provides the controls to the programmable digital delay line, which is used in
conjunction with the fast-integrating sampler for sampling the received signal.
• It provides control to the analog switches that are used in the fast-integrating sam
pler.
• It provides 13 (multiplexed) 12-bits analog-to-digital converter (ADC) channels,
which are used to digitize the sampled signal.
• It transmits the digitized result from the ADC, via RS-232, to the computer, where
the signal processing is performed.
During the radar operation, the pulse generator is triggered by the square wave, which is
generated by the microcontroller. The output waveform of the generator is a pulse with
pulse width 't"pulse typically less than 1 ns. The bandwidth of the pulse is determined by
1/ 't"pulse. Hence the bandwidth of the generated pulse is typically greater than I GHz.
If a conventional radar receiver, i.e. receiver that samples of the return signal directly,
is used to sample the I GHz bandwidth return signal, it will require an ADC with a
sampling frequency of at least 2 GHz (Nyquist sampling theorem). In order to lower the
requirement of the ADC, a fast-integrating sampler with a digitally-controlled delay line
is used for sampling the received signal. Figure 3.2 illustrates the receiver operation.
The blue waveform indicates the transmitted signal, which is produced periodically at a
rate of 2.5 MHz. The green waveform indicates the return echoes. The sampler is trig
gered by the delayed square wave. The delay is set by the delay line, which corresponds to
a particular range from the radar. When the delay line is set to TA, the sampler will sample
the voltage that appears on the receiving antenna. The delay is set to be unchanged for a
number of pulses, therefore the sampler will sample the return echo at TA for a number of
times. An integrator is used to integrate the sampled echo, and it is reset when the delay
is changed to the next value. The output of the integrator is connected to an instrumen
tation amplifier, which is used to amplify the difference signal between the output of the
integrator (integrating sampler) and a reference sampler2. Later, by sliding the delay line
1 The microcontroller is operated with a master clock frequency of 40 MHz. The frequency of the driving wavefonn to the transmitter and receiver is set by the timer module by scale down the master clock frequency. The PWM module is used to set the duty cycle of the driving wavefonn [4]. In this design, the frequency of the output wavefonn is set to 2.5 MHz and duty cycle is set to 50 %.
2The input to the reference sampler is a 50 n resistor connected to the ground. Hence the reference sampler integrates any noise and temperature drift seen by the 50 n load. Since temperature drift is present in both samplers, hence by taking the difference signal between the sampler, the common temperature related drift presented to both sampler can be subtracted, so the amplified signal is less temperature dependent.
22
PRI =400ns
(i 1\
\ 1/ \" ~ ... (
~'~-.' '~"
Rx \. Tx
V lime
Rx "'-,
.~
lime
Delay lime = lit
Figure 3.2: The UWB receiver operation
to different value, i.e., TB, Tc etc., a range profile can be obtained.
The effective sampling rate of the receiver is determined by the step size of the delay line,
i.e. the time difference between 1A and TB. Hence a high sampling rate can be achieved
by using a delay line with sub-nanosecond step size. With this implementation, a mod
erate speed ADC will be sufficient for the application. Furthermore, since many received
signals are integrated, the signal-to-noise-ratio (SNR) of the sampled signal is improved.
Finally, a user interface, written in Python, is used to display and process the received
signal. It also allows the user to change the settings of the system and initiates data
acquisition. Figure 3.3 shows the interface.
3.3 UWB Radar Signal Modeling
The material presented in this section was adapted from [57].
For a single transmitter and receiver UWB radar system, the transmitting signal is sent by
the transmitter and reflected from the target in the scene. Since the radar system can be
modeled as a linear system, and the practical antenna has a certain bandwidth, the signal
received at the receiver is a bandlimited, delayed and scaled version of the transmitted
23
I
.. _ .. """"."... "'- ..,. - .0< ...... [ .... "'" ~;<O<. __ '"'~.~,~,""
,.- ....,. -'''-M''' 0". _ g".-',,<>-nl ~....,_j
__ enI: """ ~,~ P."", ... """"
"'- <b< --=~~""'" Spoo;r.o "'" .... , r·X",,.J ... , ," ... ,. .....
.. -_ o.t .• "'''"''''''''_ ..... ~ .. F • .,.
""" . """"' . ....; "J""" "'""1Uo<l' ",-"'" ~......-,.,~
,.......,.~ f'oorl........,
'f<~ ~".)' .~ , f _~""'. ;..
-~ ,--""' .. """ ( '"-..... ~ ....
~-C"" ... • _M •
.......... "'''''-00< ~et«' [>0:.
--, -
wher~ ~(I1 ,~the impul o;e re-;pon.o;e of the scene, V,. (r i IS the tr:mmlllted wavcfolm.
S , n"~ J """",1"""" "'lh~ "m~ (~,mao" t",,'ullle, ~ pr."lucl '" Ihe frcq"~Lln domam. ,he
',i(j~ , mudd em' t>c ~'f"L~,ed ""
I.e: H,, (f) and H" (ji be the tra",fer funcllnM of tne lIan,mmml! and l"I..,<:clYln8 antenna
r~I'~liv~ly. nnd II_ri,j) h<: Ih~ impul,e re~I>"n'" (,ftt·", frnnl-end amrl,fi~r. Ihe ~ig"al
,cen h:- I)'" ta~t.imegr"'mf, ",ml'ler i, gi"~n hy
wllich IS VJlid f(}l3gll'en directions. I.C, 11,.,1 (1 ;llldJf" n ar.: J iun",,"l "llbe dorccwlII
of arm-al "r an echo,
Smce the tramfer funC1ion if"lf', JI,An and (f"",p (f) also reprcse~t the gam rC'>po~>e
tif anlenM and ampj i li~r respcC1ile ly. and the gain 01 Ihe ~Illcnna and amphlier ch.ang~
"yer frcqu~c~. Hence. for a UW B ~~~ tem. the antenna and arnplilier! trans fer function.
I.e. H" (fL H, ,(j1 31id H"",,, (j), are frequ~nc; de~ndenl funcuoll> .
3.4 Signal Processing
\-Vhell larget. are plaDed m t~ ~Cell<! , .be ~l~na l recdvN by the reN:,,'cr consist, flf ttle
ecoo.e, frnm thc tar~et. and the background clur:er. I c OCOOe<l from objects ofll(\ mt~re,;t
In th~ sccnc. In order '0 e:ttracl the locallon Mtre .argets from the cluner. signal proc~s·
Ing l.i requmxL In this socm",. me ~Ignal prnc""~mg tcchmques u,;ed ""ill Ix: d"cussed.
namely Ixtckground .ubtracIlOn. sisnJlliltcring and reJrnformmg.
3.4.1 I~"ckground suhlraclion
I n an I "door en •• mnment . lhere arl': "/ten,, 1m of reflccli.'e O"JOCI, _ other Ill"" the targel_
"f-Intere,;t. loc~tild m thc .cent. I.e. tahl",;. ch3lr>. Since the,e object, are ~tallOn"ry,
1,~, they will 001 change liS [)Osmon unle;;s someone IOOVes them. Thc profile COntlln;;
Ihc~c ~Iational)' ob}C'CI5. whICh can b<: ~n as the constant toackgroucid dun"" Whn a
Il«,flk i~ c~plu~d "ill1 I 1'''8cI-"I ' inle""sl placed 111 'h ~ ~lIe, Ike- bxl..ltrmmd pr.~file.
Ilia: ,,~> ,' ''pTun:d "a rh ~r, Ca" t>C u>cd tt'l n:mo\'~ the: h:tdcgfOund ... lu nCt', t.e Ihe crht><:!i (If
Ih r !it"1 i('Il~r) """jc~1 ... f,(I!11 Ih~ laler profik . HelKc. thc ':I.Il!et rt'SpOn..: ('>f Ihe Iar, ... !-<>f
ml~TI;,1 .~" I ... revL..,.I~d
3.4.2 Linear Slgmll Filll'rjn~
Tn.: lII},onaJ c, ,"dal"'n !('o,:h",q,,~ { dOl he us.:-d 'Il ImpH"': Ill.: S.'IIIt oi Ih~ rc<:C " ~d sIgna l
n,,~,~ a.·h,c-ed i>}' OOfI'Claung Ihe noel'"e ::l s i~1 ,,",Ih a 'I'f(rrn~ .~l~n al In 3 1\':U1'\"W'
band ~y,Il.'In. , ..... efr-n:'",,, ~, sual "11'I.1'hca olf lhc tr.lnsmH,cd . .agnal. aslh.: 5haiX' ufl llr
,ign:" ,> oonr.all ~ ~nehansed durmG ,hc.' radar operatlon Ho,,"'C'\'cr. fur ~ uwn ~ 1~na.l. th t·
>lIap<: "I' Ih~ >!!lnal " eh~ol!l!'d mnny hmes dunng t~ r!car operat;o:1. Th.:!i.<." cll:l n~ cs lin'
<lu,," iI) the t .... t Ihallh ... :ull~una hand- limns the sl~I, and multip l ~ ",n~ction occun; \\rn:n
lloe I,:,,&,h of 111 ~ l:1rgCt I> greater :han the pu lie \\ldth, 1 C LWJn > .. T,wl .... Ilene.;. lilt·
n::kllCllce S'tu:..1 u).Cd In II\!.: UWll radM I~ a rC!ipons.: of a IIlI'1'~t rcronlcd b~' the rcCCl\'Inj!
~I~mcnl
T ... ·0 linear siGnal fihnin~ mt·lhU<J . ~Tt" dl ..... ·U~"'d in ll,,~ , .. 'Clio", namely m~l~","d fill ... "ng
and inH'fSIC filleri:o.g.
r n I .... · mald'cd 1iI:(, inl! mel hod, I he n:«"i\'cd "l!lUJ j, C()fT('b,,,d "'lIh the OOIIJU":'!( of ,h~
",f"""nce SIgnal n,,, p ....... "'e'>~ " i<icnl"nl m cmsHom:l;u 10:1, Lr.'t Ihe rCCl:I,;~d \\·;w .. foml
be 1111. In .... hil" no;'-C La....,. lhe matched fi lle r IS defined ~s I ~~ I
Ifll}, ; (,
hMl '.11
1~lf)l d.
\"1-'- , 1
"ht..,r '" n "'flSlant \\h,~h ~dll he: u..cd 10 , hll1 10 .. 'I''''':'\I''Il (>fth. fI\llflU\ pea , fhe
output ur ' h~ ul~ldlCd hlt~r'~ gi" cn by
"il) .T'i _ /.o. r l .11]
1"..11 , .. (:~ •• ,I' l lt!
1\·Jr'I!.·-'"
1'he tr:mSfCf fU"'lIon oflhc 1m:." ...., fil: .... I> Jdincd as II><- .m..""", 011"," ~"U"~I I rJ us
fonnro refcrcl>re . il/n;,1 "',,.. ~ delincd bit" ..... Idth B. For a ba.....b:lndo-d , .gnal \, tile" m~cnc
filt~r I< ~'I''''~..ed mat""maticall} ." I:! I I
11,,_, I ) -
H, d !t {~~-!" ,..1 , / . ,
rwm ab<.>' ~ ~quati"n it i. n~>t~d thaI. the u" 1"T'>C lilter ~"d Ilwtchcd r, Itl" h:" e ""mC pltl"C
rc' pun,e m'el" 1'8>, b,md. 1 c, - ~ $ f S~. all(! the ",,,gnttu<!e,, ~llrer' by the fa<;t<!,
---L.. I~~ . ~ 11 In th~ rrctlUCn~y dum,,,n. th~ OUtput uf tll,: ;""cr",- filter 1< H """ funct;nn "J,' and In :U1t~ d"I1"" n. tim I. trHn:;I,,;e,1 hJ " "", ' t timet "''',
The "~ ' : r"nclI.,n h" , lu rse .~id ~lobc> In mdtr 10 redu.:e the »dclobes. the QULpct of '.he
u" ""e filter I n r~ frequency ,Iorna;n. the r.-l'I fu,.... .. lIon .• s tapered ""lth wmdo'" [22. 21 ].
I II(" "·Clg~l'. lIl ii funcl!on Ilhe '" mdO\\' ) snloolh ~ thl: edges of the baoo I~ tn.: mque&y
dOl r.u ln . "Inch mluce.lhe "delobc<J ofthc umc domam re'pon~. lIow.-. cr. the mam·
lobe o r tile lime domain rL"'pon,c I. brQ3dcn durin~ the "jndO"~!Ig ~;, Tabk 3 I
.ho""l the propt'Tlll~ of ""me ~trun'm l y 0)(.'<1 ""<'lghl m~ fun<11o'"
q """'"
~ .. - -T, ·,1."'I
1"""," .' .' ~ I " -I""nrc. 1-'_1 " ..... ,.
t·:,..I,..IQ.., • I; ., -.,,- :.. ',' ..... ' .::r
,. ",'" '"j :<111, , .
.. .' . ,
, .. :!;v.--" ,t" h. , .k! \j ~,.~t.",t., •.• , . . · . .
•
I " , · , " , ,
nO(' ~nl ... ",~ "",,,,,,,0,(' . "d Il,t 'tc(",,'tr lran,fl'r rU"Ch,~n of I J\\ 11 tad.u "Y'lcm 1('1,01 1(, lun·
oIl " "'t t~", tmo_mln.nll imp"l", <l1l" a.! HtllCC tt... "lInai ""lCa.~m¥ lcdtn",,,,, dC'\Cnbe.r
In th" !>eCI1O<!;:m IX' appl....! to the = 111 l \\'1:1 radar ' YSlem,:IS tnt rt<:tl\W ~,gnalls
bandllmltoo loa pas!ob.md., e. -! ~ f ~ ~. lllc- simulated ",suit. u>jn~ m31th .. d filt .. nn~
and in' e= fi ltC1inl! = .oown in Cb3f'1l" 6
".·k l Ul' lllllrOrlniu;! ! . \ rra ~ Th('or~
\\"hm" J"'~ar 8rT':!.) uf =e"'e", i~ u~. It I~ p.'s"h l~ 'n 'e,""I,'~ !>."h rans.e R alill allille
of am",1 e uf" la'l'ct III the "'·l"JlC F,gurt 3 -1 Il1u,rr.,c, til : l"'uonCl')' ,'f I hlle~ ' a,,3) "I
r:-..:C" ·,nll <'kmcnI5.
•
• , ,.'"
.J "
• •
"~j;UI1lin~ a pomI131"{1~\ i~ ~nu1ttd ~umcic:ltl ~ f!lt from 1M r .. ,hr. t!r .... ~'er'OIlI ,dle'leo!
fmm the ]1fIml \M~e\ can ~ uppru~ lm~t~\l as 3. pll\l1!1t """',. when It ,.dchn the nc,'("t\·
"'~ dements. I,om F,gurt ].4. 11 sho'-' 5 thaI tho v.a'-.:fiunl !Il"Iiv:s at ""' .... h ncCl""·'" al :I.
ditTcfI:!I' !lfN.'" dcl~\" The I.me lhllcn'lll"t bel" een l ... u ,wJa..=1 'C'«" ms. <,Ic "n .. n' ,:an I,,"
calculated bv r ,.. I.":, ~ I . '" hen: " ., :h<- tI"lana ""',"~:-n .IK '01.1 .... '1. .. 11 =.:"' '''1> dtnWfll.
8 il; .hc :an~1t of am • • 1 or 1M ,,~.,cr"'nt .nd <" '" th,· )ptto! ... r htilil ' ''' J " lil~ 1110'.)
Th •• 1Lmc' diff"ert:ICc CM ~I,., Ill- e~prt" • .ctl b a rim..: <I"n ocr", ....... " I",," 3m)' rlerne'" lIS
IjI "" ~ ." .. :: 11 1. "'h~rc.1, " lh~ """ ' ~le"J!lh R)' _u"n"" 'lIlbr , ... ~" ... I .,~ "al f".." allll~ ,,-.·C" "'l! elelncn!. " ",h app""I,,,a.e dela~ ~I\d I'ha~ ~ompe~tI"'''.1 beam ma~ he fmmd
'" ~ p.:>nicula. dU'!'C110r..
SlflCe the :mjlle or am'"lIJ ur:be !tlurn t • .'hu from 111<" p'",m I~'~t I~ "nklmwn . • bc-.m
'itC'CnnB aJjlonlhm I. ~ to f,,,"u. Ihe ,m;lgc rll!lu r~ 3 ~ , lh,.tJ31C' Ill, he~m Io..·u,mjl:
Opqtlllun. The bc-~m .. ',I] l..: "cel"C"\l th'n) - s",,, ,,, /I""". "I'e'e all p')i "l~ .Iung " I,,,n,c·
uia! angle 6, ""n}oc, c,,,lunted h) " ~Ia)' an,l ~u",' heamIDl1n l n~. ""nh arr"'l''''~ I'M<l'
... -mpcnNllou" J ' Ihe pm..~<s'n~ '" III I>c 'kme" on ha ...... han'led d313 I I.e ;,pc=ctrum ... f lh~ ra,,~ ~"""rr.~~d d:na , <, flr~l tmll_dated 10 ba~bo:Ind! . !'he fo.:UiCd 51~I1 QI at POlOt .". 81
... ,tl~ 9, ., eXl're,~ as [~:: l
, , 0"'1""" D - 1 t.ll - ro ~ ,J~~"""'''/il A
~-"
•
~tr.ly. '~illl~ Ihe ba.roomkJ M);nll f<.lf rc~civcr II and ro 8, is (h~ liln~ .lela) frnm locu\cd
poinl II at kIllKit 6, to thc rccc"'m~ ckml"ll\
Since me 5i!:nal ;5 !lruT\pteJ at dl ~rclc pmn(s al",,~ thc array. l~c spa,:",..: h!:1\"C'" tk
alTa~ d~menl) ne~dl. I\J be smalt c!\OJu):h 10 ~wld spahK\ ahaling [21J n,~ ' tsull of
spanal ahr':ilng I~ kno .... TL as Ihc "~"'tmJ; lube cITect'. "here Ihc lob<--s arc rq>r1lc<l a!
$~\cr3 1 3nj,t lc5, wilh the .amc amrhlU.Jc jl) lil<: m,,,r. 1<.>1:1,,_ To ~~lIld "c'mpkld~ '>I'allal
aliasing.lhc alT1l~ clements an: rcqU; tN 10 be ~""cd al[I;." th." i. '2. 11 !I" '~quirc"'elll
ii no( mt!. the flri!\ "'I1l.tjn~ lobe (.>l'cun> (."th rC~f'l"(,1 to. beam un t>orr:s'J;hll "'h~" 1he
rhiISC ~hlft between thc alTa\' clement I~ ~r. In1 S.'h·Ul~ fOf 1!.I;W. - 211. II ~,dd<;
Ikn::c. thc lTUI\unulTl ~~cnn!l ~nglc i, bmlled t" "heft" '/x-I,hIIM" shih het",.,.,,, lb~ array
ell-me'" j!> r. /22( Sol. Ilig rur U ~,"jI = If. ,\ )'Ich);
, " = W'I'S'''( - , ........ 'U'
I!I the l'WB lIDpIII",,· 8mtr. d" soalml: I(lhn dle~'1 j< ~I)<,en, Sjnc~ ,"" ~pc..-ua! .::ompo
nmlS tlr. ",dd,;,,,,' ~I::uol '5 ~l'rtlOd V~CI .la.l};C ra:lg~ vI l'cq"""e,r:<;. the g'.''''1: lrthe,
.... "Cur H! d,ne.<1" al1!lr f"l. d'fTncnl f.e<l llt'fIC)' Whilf Ihf maull,,1lcs are H,hl~rl cohc:.
mlly. the grail"!! lohe< a.e QvcraBetl o'er the Il;:qucn<:) spci:lrum limec. ,he gr.llIn~
lllhrs at'~ suppres!>l:'d [451. Ftgurt) ~ tlks:r,uc \h'$ phroommon. wh~c flllCi.'i ami [w ..
are the amI' focusC'd bc~m iOT t. tJ;h frcq"('I"'~ CUlnl"'Rtl1l all" Ill" frctjH"'''~ ,,\"II"'"CllI
<>flhc impuls:: . cspn·II'c!l'_ A. l!lllftnotc" III F,g~rc :;,~, the (tl~i"k>be<; tu" <I,lfe,,,,,, f",.
'1l1cocics ~rt loca\,," HI ~I,c .... nt· ",,!;ic :1110.1 art' brill!: alllle" r"n'truch~ely .... h cI~ as the
1!",ln'g loI~ arf ,~cu"rd .. , dltf~ • .,." an!!k~ f,)I-d,fferent sl~nnl f"rcquenc,cs, The 11115
al ignment <of lho gm!mg l"be a,'eraged the lobes over th e frequency spo:C1nlm
C,..,..,,,, ct ... ~ oddll>".
F.gure 3.t. rio< .ilu;;rnl1r m":ahgnm::,, lOf :11: ICDI in); 101m. m Ihe l~'(' ,· f UW8 ,m""I"" 11m.) sy,;cm
Amuh""" M~ \" lool B[ Ih" 's ",lh,· I"I!~ ,!,m'Il"'. Tllr c!cla~ and ~um bc~mr.wmer ahgn_
,"C h,,~, frum ~ rartlCular ,hn"""" ('1' 1'''''II •• n H. (;1)· t. ~a\ If the ph~ ~hll\ IS an u\lcg ...
llIultlPic l\f21f ... ,It,· gnu'''g lobe angle<;, tht dal J ",II nVI~: 1'["Tt'~l ly Um.": wl!lncd iOt Ihe grill ing I,.he- d" e-.:,inn" III<- ,~ n g: rrwlut ion I~ ,ufficicnlly line
JO
.. " ~-- ::-±'-, .. .. ' .. ..
,~
, .. ro,
•• ..... "
., - .. ". ,. "
., ,. " ,,,"-co. - ,' .' .,. ~ " ... " , . , .. , .. , .. I ".,,~
." 1 '. ,,,
." .. , .-
"I C)4 I'i<~ h, 1 \ V. a',,! ('7 ,_, r"a'l'-~d Ih",,,~h II,., 10'1'\' V2-RI~-C7- f( I)-·Grouno.!
"'11"'" ~ l(a) ,I""" Ihe "m"I~I~J "a\~f()nn 31 ",,,Ie ( 5-R 11-1)-' and ~ jll~n: 4 l(h) ,h",," ,
11\<, s imlJ lal~d "",'oI;lrm al ,1M R 12_1)-' .{ 7 I h" "'I"~~ ".' et; .nn <h,'" t1 I, igure 4. 'ral
alld 1"1 is Ihe ~imllialed:"o MII/ .:Ir;, Inil ' ;S".I Micm_1 I I' "" nu lalor i~ I,><:J fLl r Ihi' dn;u,'
simulal ;<>11 Dnd plnl~ gell<:rali,-, ,, .
. -. ,~-
_ ... _ .• , _.- _ .. ..
I i
•
,
I .. , . ill
• -.- .... ,. -- - " ". ...
·\11h.: ill'la'Kc "hen tI>~ 11"3,, ~i'l,'r 04 '5 V"i~f:trM . the coil": l"r 'ulta~" is o.Ir,,1" In,",
al'l'""illl&I~I~ 15 \' 1" () V. "hid! 0:,,,11. ;" ~ · IS V drt,p I'n ncode (I·RI .I·D.!. Ihi.
c.,,~, lht ..... h •• l1k, ,Ii,~k I)~ h' '·'''H,ho.:!. alld dNha~n (7, la R I J. RI4 and Impedance
\If the anl~nn.l. Ka. h'''MJ 11 \' l"he ehar;:mg IImr ~<,"'\l~nl of (7 i~ Ippn'XlmalcJ)
r l "'""",0' '" (~ (RI4// RU li Rl'-' .'" )01'" I hus ~ nega\h e puis.- i, &e nerilh·o.I "".""
the ~"\~""M ked, Fig"o: 4 4 ,""" < l~ j1(~erated pIIIst- and F ig\l~ 4,5 sho,,, ! 1!ic 1 WI
an.:Il}"~' 5 ~pmdl ... ~d ,n .. ll 1 ~ 71· , he ",(·»,\)", ,,,,,,,, 1) Blld I ..... OfT ana l)si. was poert.:-rrned
usinf: i\8lkm Intini um 5JiO li\ J)~O (dllli~,1 't"':1~e ""ilio'>COpc ) From I isure 4.5. II
shoJ,. s Ihal lhe m~~sure pul.o;c 1:>nn.d" iJlIl "IPI',,,,,nWl.ld) 1 G f 1~ 11"" CHT. l.'1i, .nal) )i ~
i, toand·limitN tr~ IIIe r>so u~<J, ~kne~. lI.t han,l" ,JIll ,,' II" .. H.·nc .... IN 1',,1><: ""uld 1M.
" iocr_
, J
I " , , I " 1
f ;1::UW ~ 4 n", ' '''11'111 "~ I d.,.,n fr"'n I ~ 7 ~ Ve rt ical scalc. 500 mV'd 'l \" "h 0 \ . OtTs<:l) " u riIOllt. ' >Cllk ~ 1I ... ·di,
I-T-r- --- ,--,
F'l!.un: ·t ~: rhc UUlpuT " "vdo'''' Ifl)'" I ~ 7 J .... nh Ilf-r anw l >' ''~ t.. " calh Ilmt-o.lornain venital K ale: ~oo mVldil ( \'I Ilh -J N ",I; o tTsc!) r;", ~· d"'m:I; n 1>o.',;, <.>nl,1 :;c" lr ' <0 n, I)F I "...,ital "':dl c_ .20 dll on .';1 ;\ Dn horiwnlal ~'3 1 ~ : 200 MI I-tJdi, Ir~"~' 0 ,,, ~ G II ~ Cfnln:: po;:>5i l io;ln COITC' J'OI1 i.ls tn 1 ( i H ~ )
re, .sC'd ~ ireu;t d ial!nlrn. ,,1>;, h i, ['I'o.lucnl 1.1""1' K,ud, ItS ~nd C6 11'" ~ I" !,:<:Mra' C'
11 I;rn~ .kl ~~ " hid! i~ ... <;coJ In "uteh .. Ilh the IIlIli.1 ddD} ~ b) tho.' di)! ilaJ <lday I"", in
Ih,- fl>l·,..tq; •• 1 i"~ ""mrler (oJ~",,,he..l .n -;e.::U,," ~,I)_ TI>e .. nl>er d\.1.~es arc aimed to
~~t1,craIC a ,in' dar hut ,h,,'ter puis.: , ",t h a hlghC'r p<'11. · I..,..pe-ak whage .
.. -'.~ . ~. -
figure 1.6. UWIJ pul~ 8CIICfIlt« o{ c ircuit di~gr..m
I t", b~",h"dlh ",f the pulse ~N"''''JI,-J i ...... , C'fTll lned b} tl>e sh:lrpneu (riKlime\ d I~ IriG
~n"'t; ~"" r~ " ., ~ dn' , ng ('~ .oJ R I anJ I~ lI"lInS,SIOf bas~ impoedance II>e .~hl'l'oes<
"I the ~uare "3 '~. 1"I>C'lhl"f ",ilh 11K- charlK lerislic of I I>e mlnsi~,oX u~d. "ill <klrmur>t
th" <Il<'ed 01 ~wi , c h i,,& ,,,'IV,,, "hidllr~d~ tu ,he ~h.''l!i n ~ ft"d disch/lrgin~ ~fl h e OutpUI
,,~, efinm. II>¢ ~tnrht~ 01 III<' jl.cu"I'II ,cd puis<: i~ alf'""t~d b) the r.:~p\)nllt (,f thi: clur~·
'"~ CJra.::iIOf ("2 in 1M h'ill t~"c"C) '1l<:"Cln,m.
In the' rol~"n{l ~"i",". the Intf'I"'l'C'm<'fII' 11\.11 are l>etfum~d 'a. lhe r utse 1;,n..·rnl,'I"
" ,II h" di5< U)lffi, aoJ rt:'Sults "ill ~ pr~lltN.
·t2 Triggerin g I~dge of I he Sq 11;1 re \\'a \ ('ror m
In I h i~ d~,,~n, 1"0 1"'enn~.lIK 3nd UID. are lISW in paralld to shonen the rt~· and
,,,11 .1 iHl~ "j lhe "luMre wa,..:furm.1br A~i kn' In/inium 5·H!]JA DIiO is used In _asll~
Ih~ Ir:tn.ili"n li,n..· Ihe 9wr..gmg 'i'fl<Cl,,'n nil ,he DSO is $C"t II) ~'mlj:r man~ pulses. on
"hith the In~on Ir~nsili,," lin~ is nhlained i"isun! 4,7 "nJ I i~ur~.1 8 ~ho" the "bse .... d
riS/:_ ~nd I~II-"mc l f('I" lhe ,~"" ,,(,. ,inglc ;n~~ner ."d M I"·,,, p.llrulk;1 i n\· ~ncrs,
I lIr,. ''''10:10.: " '''."rtcr. ,hr I ~;'· ~ ri~ ·li~ and fJII"Itll( are Jprt() ~lmtlld~ 2.2~ '.' and
100 n' ro:.~"1i,rl~ In lho;: ( .. ~ "rt .. " p.1n1 Ih:t in"~"C"n. I~ r;$I: time and fJII'lIme are
~ppro),"n:Hel) 0.91 n~ and U.M !I "" <C'>fl<'I.", d } n". , lKlI" Ih~1 the eJi'~ or I"" square
\. ~. e in ~t>:'rpc'ne.:llhroul!h th,s moJif"a,;" n ... h,eh ;. d~ I" rl.e l".;rr~'>C III ' "m:nl dri~c
,nl,' Lh ... ,~p:r('Hur ('5. " .... n '''0 par:tlld im'cnelS are LISN.
•. " II. ...... ""'~ ,10) •• iI_tmt
The BrG~:!OW:X Rf 1fon"~,~mf was II~ to rcpla« the ''''''SI.lnr H~R,}IA . that was
"set! i~ [~;l, TBf>le 4 I " cnnSlruc~ed to cornpal"(' :he ...-rtonna"cc! l>cI .... c~n the!le IWO
Rf Intn>l,lor Tahl~ 41 rJ,o .... ,; thai BfG510W'X ba~ ~ \<J>O.'er rr1:"b;>c~ .:«I""c,[:mcc fllc·
h, ttn cnllo;-.;lnr and b.:\...: of the lr.msislOrt, which enabk~ a ia:;ler ~w,tch"'l1 :oc1nm than
the UFRI) I.I, RF [rAnS,lam Ille OO:JlIll wave ob!ie:'\'w on the DSO. shO") a m~!n~lly
' ..... ·r"ue !n I ... peak IIIYIplo tu:k The ...... are m.:m)' other RF m;)$lstors "'Nch ha~e io"'u
t«dhacl capacna .... ....,. hOV' ,,\~I. 111~:II th:; "x...,~ of \ow ,olltttor-emHttr hrea~do\l"n
lohagc. I.e 'Yf»OIlIy I~s~ than 10 V. ""Inch 1$ nol ~u'Iat>le fOi thIS de;;lgn.
Tab le 4.1 C"tnl'armg the perforrt\a"".. "f BFG~20W:X 3"" I:IfR9 1 A [16. 17[
4.3 11I1C'tdigiial Capacitur
me charging capac;lm ["2 '" hgun: 4, (, 'S ",~p<-"ISif>k 1<". Ihe pul".. Mnpillude JnoJ pu l..:
sh:tpe of the @ener"Ied W.l' "fmm. A II capac;l(J~ haw an mduc'm', c,1lHllnllent In !len,'S
w\1h lhe cap;rcl:ance cOffipooem. The mductl\'e compon~'I11 cau~ s lin Il"ICrelUI! ,n lraM·
mlnlOO k'!iS wh:n a hlgb~r frequenc), signal L5 applied III Ihe CapaC,('" [42J H~nce II
I!Hp3crLive dement wilh lesi tndu.t1l·c component ""111 be more ~ul\abk for g~nera""g
v~ry ~hort pulsn.
T", n capac"" e elemml~ '" nr in~C'Sti@~ted. II) the surf:ltt mount dill' r:ap3dlor, .... h.(h
. i ,,,.le I)" """d in prim,,.j em;uil board ~mbl~ ,PCB). and (21 ~~ l:ltenhguaJ ,apacnot
(tLX ').
fhot- [lX" ij; ~ m;crru;tnp hne ekmt:nl. "b.,h ,~ ,,'-Cd fur protjuc:mio: 1mall C1tpaCllan«:i.
F,gun' 4.\1 ,lIu .. n.1C$ the £",""'etry or." I nc The e;I,pilCl"'"l" of Iht; tOC ,~ rJncnnined
bv tile Ih,d:ncss, le,tgth II.) and ",dlh (II '\ or Ihe I.>.>nduClul1111hc m..-fihlnp Imc I. Gen·
"l1Il1y. ",he:! lhe ch:uxt~muc rmpedJna (/.nl 01 th~ oonduc.", IlICre:l>t"'o. the clrc.:h,,:
C"1ipacilancc d~w,~>. funhcrmore. the ,ap:ICI~C I~ IIIUI ,ncrea.o;cd ... th ~ gl.jli> he·
I ",·et:n Ilk ~ondll<'l<Jr> "nT~R5C Fin:lll)'. II!. 1M cunOuclOrs 11ft' mounted on a ~ub.uate . ~c
th,ck,,.;,;s and the d,eitt'nc wn,l:m, (t.) ut" Ihe ;.ub"tnUc dft'(:1 Ih., effectl\"e capaclIana:
oflhr rondUCIOI'S Pl.
Figure ~.9: Imcrdig;t:l l c~p:ICiHlr l,l~omC11)
rill: c~pao:iunce of III<:: I DC Cln b.: C>\kulalcd u~i ng [,,11<;1\' i n.-; t"qual;un~ ot>ta; ncd from
1~21
. Ii." (kl In=t:/1II I E' I-
K',k'i
,)f II" . - ,,,"-, - _ .. _-\ 4!1" +S
,,'=\/ 1 _ .. :
where II,S Ihe numher of cond\~lol"!I. l is Ill,' length or ~ach conductor.)j is Inc "idlll of
l-:lcll condUClor. S i.> lhe spacing helw.:en Ihe ccmducl(>r and i y is 110,' r" .. rmiUi~ iI)' (If fre<:
space ('" ~.854 ~ 10- 11 r -m I. Thcs.c equal ions a~sume Inal the III ickrn:5~ of Ihc conductors
a ..... 7.ero. Ii." I. ~ I is a c{)fTtplc te ell iplic inlegral "hich can be appro~ imated wilh !"(lll"" ing
t:qualion " ith ~n ~rror of J% or I~ s (.12.1.
lhe d ilfcrcn.:.: bel"cen Ihe calculated capac ,UIIl':C and the aClual cap:..: 11:lll<C could re.ull
from .
• rile c"nd"n",~ ha,·c a ,mn_,eros Ihic~n<'S.\. lienee Ih~ aCI"a 1 capac ,lartee could he
higher
• A ..".,.11 un'''",,1 nf wt>'t,~tc i, rcm,we,1 d ,"""'g th~ mill ing 111"'10.:.:,,1. "h,~h rc,,,h~
in a ""oller ,opaci!~"c" tha" Ih~ "alculated ,~I"c .
Tnting t>, '~nl, arc nmtl~ I" ~otrol"'rc Ihe f'I.-rk.m~,,,-c OC! "',",ell ~ mull i_la) cr ccm""c d, 'f'
"~f'.ci l,' r a"d a" 11)(' ~ ,sur" ~ . II) 80'"'' the k--.I"'iS ",·,.,,,1 mad<.- lor Ih~ 11)( nl~ le'I'''!:
.... ,~n:l I", a 1.5 pr t crJ,mc ch.1' ,apadt()f ha~ ~ §II",I~, !a)nul. Tht:' IDC 1h~1 " m~d.! ro"'ii<t~ 01 14 cumju~I("" (t;ng~,sl. "hi.1I an: ( ... ml,·d on a I · R~ boanll£, '" 4.3J) l ilt
dlmtnsiuf\S ur lhe 11)(' ~rt: ht;,.J I>,, !o"
• \\ " lIh III 11K' wridu:1OI' -/U08 mm
• SPl~C bel,,~n ~ NIIducwn -IJ.:S~ mnl
In /\<lie..- I .. '''mr;.n: IDC "nh the: tllip c3pac;Mr. an "~I nlo;;t,un:nlCnl fVl' bolll boan.1-
,,3.< jl<=rf" m..-oJ ",III Alo' ilcnl [50 710 ncl"Of~ anal~n:I h :i.u1c 4 II ,I", ... , Inc , ,<'('l.il
:l iag. ... m arkl <iq,i<-1' 11 ... • <;21 mcasu~ml'111 condition. "Nt I 01 tllC '''':I",,,~ anal~''''r i ~
repreS<'nlcoJ II) .' "10"1,,1 ,",,\I"X ... illl 50 fl resiMClr, and [l<ln 2 i ~ '''I''''-crtlcrJ 1» " SO fl
res istor 10 ground Ill" ''',o/iS" ... !iu" is 3 hisll p.1 !.5 lilter "'III n Ih'~-'fCI;~al :; dB c ul ..... IT
Ill.,.,---J, •• - ", I (iH, -~ , "
PORT I 'M PORT 2
The IQSS ,n lhe p:lS~band III .he high pas, fi le.: •• runlled b) It..: chi p cap.1cilUf and ,npu1
,n'p.:wn".., ... r r un I and POrt ~ Ilf L~ n<-.. "Of~ a .... I) ,,,' . j .. urrn'),imillo:l~ 8.16 till al
1 15 GH£. B' .-11'-''''' in riJl.u n:: 4. 11(a)_ Ccmpanng I.} Ih/: " 'b rJ ll .• 1 t }6 GHL I ... " oJ ......
to tile' high p.u$ filter fQrmed ,, ;, 11 as> IIX. ~n on Figun: 4.lllb). prou's chal the int .. ,·
,Ul1ltal C~",""""r ''''1'''",,$ In" "fli,cl"""~ In pa'~"'8 t"~11 f~.......: ~ ~I~ .. I~ I' "nhoen" .... c.
IOC pa~"oJ u,..",," III rill"'" -l .12tat" n .. , Hal . and dlCl'c " .. n ... ,,,,anred O!'><,"ano:r "1
1.52 (jill.. "hId. tl\~le$ ., , .... " ,uhl" f,,,. ,...- ~l'ph;;:"IMm
•• •• .. • • .. ,. •
I
hllun: ~ . I~ ; Comparin~ the S~I IJ\.::lSun:mCflI for th .. high pass filll". usill~ diff~re"t l~pa,· il<.>' dem~nr The A-"XIS ~p~nS 1'1"'11 ~\')('J t.: IV III X ,~ (ill] n", )-a.< ,~ is IOdllidi._
The ,·apa,-itan.;.' 01' the inl .. nli~11I11 ":'Pi!I<: lkl ~an 1>(' c~imalc,1 "',,,,, I, ,~""" 4.1 ~(h)_ I he
CIJI-otr freqlX'n.:y of the hi~h pa~j illtIT. fom..:o.J "0110 11)( lnd inpol ''''loe-;l .. III;c IIf I',,!! I
aod Pon 2 "fl~ n<;t"On. ~nal}l..I:r. i~ a"'I"""'ltn~ld~ 1 t .111l,oh.<t1"\e\1 ,'I, (I\e , ~""rk all
Blyzer). The \"Jp~" 'lam'" ,,1' the ILX" ,J Il 1:>.' .aleulale u~<"s tile "."up "'"'" .... n <" h[l.UfC -l \ I
~
The m"asurW ~~""· lIa,>c .. "1 1110: IDe i, JI'I'N."m"'el~ ~.O·I. h,gh« lhillllhc C.J!cOblcd
... h ....
I"gure " .1_\ $hoI' S lhe U\\ 11 puls.e St'I\CMlt, r boMllllill 'us maJt:. "11,,,11 ;, ba ... -,J on the
ein:uil cksi ~,n s"",,wn in riil"r .. ~ 0 ri, ...... 4 I~ ..oo"J the b'<"1"ll:rJlro p" tse , tl>""f'o~-d un
the DSO. Comp";n;: lu F, !o:tlll' ~~ . 11 ~ho , .. , lin 1I(,p .. ,,~i"'lI1<,ly 4~O ,,,v ,,,,rell«: In Ill<.:
puis.: ampl itude ..... bile nu intll;n II .... .. ~m, .. f'UL'< "..JIlt TIwo Il~ r 1I"3J~ .,. (I' 'g"re .l. 15)
,110"" •• i~".lI ba,,,I,, ,"t" "t I (01 1 .. i< a~ ho::'cd " ,Ih Ihe....,,, ""Ik SC'"",Utor Ik."~\",.
tlo..· tn.t' , ... liIe" loIt" is d".nc .. """ the IIUC puiS(' Illnplm.,;k is ~:Il .. r than thai ubSt'f'o.-,J
" " tile ,,<.<;Wu":''JY'
'"
rig""", ~_ IJ · l W[l pul>o: ~cn.;ral"r PC13
I ,
figure 4.14 . The measured ... a>donn at Ill.:: oulpul ~I Ilk I'~" pu is" ~,·n"ral<)r Vcr1k~1 ,calc . 500 m\l:<1i\ ("ilh (J V \'tT~ct ) Hl'rir.oma.i s-::aJc . ~ nv·di,
• . . .. .. ',0 • r ,"
. ,
Figure 4 15: Thc-lrn:a.5urcll "8,~r<m11 at lh~ t)ull'lI' ul ,k Th:W pili,.. !'." •. "'\<" \\,11i I)~·I 1lII31ysv;
T,m<'c-<1om.aLn vcru~al sc3k ~OO mV 'dh (wnh 1.180 mV Urr""'ll
Tlm1:-<iOlILllm hOr1zomal >C/Ok. ~o :1 .. ,1" DFT 'tn,,,,,! ,calc. !U dHm,d,,' 1"0'1111 -, ~ dBm off scI) LIFT hoOzo"t.l1 ~ak-_ 200 Mfudl' ("'''gc 0 '" :GH~. W"'I"(' f'(>s;unn l:<lfr('$f"l!o.1~ iii
I GHn
Chapter 5
Multi-Channel Ultra-Wideband
Receiver
In <).d,>, l<) rt"c o,d and dil!i \l7~ th~ n'n'IVIn): w~"~r,mll accurille]V. lh~ =pl m~ r.m' of l~
Tl'ce;'e, mu,! b~ al lea,( I",icc 11,.. hand" Id lh of the n:c~,,'('d 5 1~n31. for 3 blnd.\'milcd
~ l l':na l. r" f an l mpu l~e radar S)·'1Cm that uses Signal ... nh I uS pulse \ddlh. 3 mlmmum of
atJ,\1I1 Z Gl lz sarn!,i,"g fr..,qu~nc} i~ r~qu '~d for ad"'1ual~ proc ('Ss ,n~ arid dlg'II~IIl!l 01 lh~
n'cnHd ~').:nal If a ",,"wlIlJ{):lai !\.,<:~,,·cr d~,i~11 J. ",cd. 1h'5 """lIld Impose J 'eT) IIL,;h
samp]"'ll r.lll' ""quIIl'men! fo r til<' iU1~I()g 10 dij.!i11ll e,,"'"ene! I AI)(').
One ,'I rna:1) \ ... y.~ to .~1mple a "'ldcllailli "1I11~1 II Ilh,,,,, 11,"111» )"lll' ,arnpilllH ",Ie f\DC .
" It> ch,mncli,,' Ih~ n.'H'" 1I1l: ,;)11131 IIlto ~''\'c ml p;!1\ ' and \I.e mull1fllc ·\DC Ihcr.:alla
In] Th" ,'an ~. JUnl' l'uhl'T III the in:que:IC)' dom~1 n <l' 1I m~ d<'maJn
I (i~l z rece,Hr. TIK- duplner. or tht ~liannd J ruppinK (,her. 5q:I,,,,.lo Ih~ >I~I mill ,t\:Ij", .. "hid, fit "lH> the .<lw ..... hallncl b..nJ .. kill" ur o-~OO Mi lL. ~OO"""'OO !'oIl I ... ct ... The
requ,,...,,,,,,nl rur AD( ,. dnermme.j hy ,m, ,,,tH:h.lnnel handwidth. The prnh!em of lI.<tng
:t fr""-lucl"":Y dornam chsm,cl'7.eJ rcct,,'e, ;~ Ih~l rhe d"l' lexers are e~pen.<;"·~ In u<\dlloon.
th~ dupk" cr "'>cd llI'c<h 1(1 l~t'c. ~..,...,d ""I'Il I<o<: '''<.po" .... Dnd <;/urr CI!'otf. 10 lvo ,d <lg.MI
d;slunion [37]
...
. --
--- 3-f-----. D-------[}-,--~ -----r-
0 -"'~. f--- ••
f--_ 1-1= -0 -~
h~"rc 5.~ The lime domain c h.lIlttdi7Cd Il..::",~er fM 0-1 GHz ~,gn.al. [n].
F,S"''"'' S.~ shuwl the lime oorna ,,, cha'trlcli.ed rece,,'er IlfCh tlecru~ for a U In I GIl7.
rcct'l'·c •. Thls ~,dmaclu" IISCS rnulhplc t"ne delD} element\. ~ lime delay element
pm"id,-s a lime delay hei"' ........ ,· ,1$ " ' tlj>llt ad ,I.' IrIf'Ul I-.ach Ume aclay elem"m has a
dllT"rent ,311,10: r"" ... <I""",," J.e 0.5 1\1.. I (I "' , 1.5 tl~ t1I: •• :mJ cacb nf the time delay
cnrrespunds II) ~ r3';j!e '"aluc nl Rdrt,. N."'" - ' • T ... ~~ ,0_- rile return SLgn3115 sampled
by lhe K\:""',,r ><l dlKrde III"c ",Ln',al<. I e. lhe OutJlUI of the O.S lIS time delay dement
,.thc: sampled ,,,hage ol lh" , .-tum .'g.rul DllllTk'" (\fO.~ M. lind 50 rorm Oy 5l1mm in~ Ihe
('UII'IlI or ~'lIlp"'r\. i.e . AlX"s.. a ran~e profilt is oblaineci.
1 It.: ar~ h,le.:;lllrr s ll{l"" In Fi~urc 5 1 :;.1mrlcs II", return "gnal d, • ..ell}. II. h,eh mll1im'le!;
lhc possil'rlc d"lo" 'on u f the siguallh.1r COLJd ,"",em hdme the .~arnrJtng proces •. Fur
rh\"flunl"\':. \h , ~ '~c ' ver p,e<;<'r\'e<; ~ in.'LanL'Ulrous I GHz sl~nlll bandwidth.
Ttl.: ~amphng rIL" of this n.""civcl tS lire 'n~tr1i<' or the dr lie'mce '" 'n'I(".delay htt" ~n 1"'(\ adJlto;mt d,,1 ~y elemenl. ,.c Ardd" -.,. C!! 0.$ rI'> Ilnle-d,If"rencc t>et",~ dela)
elemen13 h cqutl· .. lenllU ~ "'mpling ndc oi 2 {jHI I- .. nhetm"',e. the number" nfume
del~y cictIKnl!> LI>~"'. lk-'cnn"'~ rhe '","""num 'titJrle ifullihe rec"I"CT can detect. for D
~ GHz ~mrh"l:: ire\j~nc~ ,O"Ce"n, a to)t;lI of I'; ume deja} clemtnts. "tlh :lr r ... t.o'\"" "'0:"O!- ns. Mild "'1)( '. are le\jt.ltred lot dnecung a rt1.l.XLmllm I':Inge or I m
figure 53 ,hows a on.In·, ,·lrt'\lll [ .. O[ .... hl ch ~on~lolS or a mllllml delay ,lnJelU.". lI ~mg
~ potentiomelC< .... ,'h ;I capoicilUf .• "<1 fi~u .. c ~ 4 ,110". lhe: rca-Ive' CIfCUI! "'uh ~ van cap
dIode dcl~> line r~11 added 10 make 8,. d';("1'runlcally a,~u.I3b1e Iltl:ty. OI'lL~' one <lU11f'1e
IS l:tken per PUls<.·I"'m.mitl~t1 al the II!TIt: ""I by ,he- o.klH} I,ne Tk 10 of cap-.: ilo' ~ ~ I C
char¥ed '·I~ a ·sample;md mlegra!,· "Pf'TOlld : C.-.:.pIHHr.c:d In mU'e <.klill In Sc.:llOll S 3
Thl- t1d~) > ~It gClIcrnted t>y varying Ihe R(" lin", cOIl,I:Jnt ttl holh dc"gn.'. The capnel.
IM)<;e of Ihe .'an"ap diode Can t>e \'sncd hy changing lh~ \nh~gc ""1'1)." Ihe VUlcap d,,><Ie.
T()gcthe r wnh a rc,IHOf. a compliler-C{'!l":rolkd (8 »AC I~ u~cd to COntrol the voltage
a.;TUSS lhe '·~nc~p t1,....J,c) delay lone "ia, dc\ cklred [51 J Th" PI'I" Ide' a m"re '(>Oth' "',..
1"'11.>11 ,,, h 1'$d~1 rflngc prulihng ~J~tc'" than the mWlual delay hu., de'oC.i~1 in I 'n)
'''·0 1 " .. T L ........ ,,,,'...c.. ~ r ue,,,-_-,
"o'f;:~'t'~'~·~~'f>"·,f. ,~ ':~~no. dJ"'·_---,~, ... ," '"01' .. t ~ '''~'''' "'~..... .. ... , _. ---rf"'''''f-H._
~ .... - "~.,." §l ..... ~._ .• _ ...•• ~~~ ': '.'.-9,r .-.. -.-,_-1
r'·'·:':':=1...J :.: ~.~ .. " .... ...
fijl:ult' 53 Tk ,.IdlY line a",lltIe fa'11>IImplcr If\.nt~ [3D)
In rh .. tt>e>l~ .• I'rogrammBhle dlg':.illlda~ line i- u ... ~1 ",th. rc- .<,('d h •. <t."'1Cgr~l,ng.
'1mplrr t' llu'e ~.S ,II/""'~ Ihe hlock dlapolm Ortlle I\C\\ . ~".:T. In th~ [oUowong leC,
nOn!;. tile !UncUOI'I of each moduk l:l ~ m:cl'er ,,·,11 lie exp1auled
5.1 Programmllhlr Digilall}rla)" Linr
lRc ..... ge profiLt is obtairr.c:d b} ch:.ngillg rhe time deJa) procIuccd by th~ &day hnt. iu
d,5Ct"CI~ .t<"P~. Sc:<·er.oI hundn=d pubes ~ IYPK"llU} lr.m>l11 'Iu:d The tl'lwc. olUllpltJ alld
I!ltt¥mtcd al ,t>e 11lII1I,UIar ,IeLay ~l,lfT"'rundmg Il> ~ Sp«"Ilic 11I11!C Ikr",'t" Ille lIttunocy
ami ' Iat.,l>ly MIlle 'lelay ekme'" ,., 'CI) """",!tant. 1lIlllkliuC>n, the "'er ,!;C or lhe <klay
ckme:1t delCrmlD~s tl'lc efiecun r;.m,phn~ f'rnjueocy j.. of!he rcteiver if, - ~,where!J.J
is the step size oi Ihe delay hne1. therefore 11 iohould ~ small tnou~ to pro, ode a sum· ,"cm ~on))hn~ 11I1~. The ,·~rica)) diode delay lone in rlgure SA j, iooDd not well ''' Ired IU
tl". aJlPhc~hOf) "" lh ... rcspon,;c of the \'lIrx;a;;r diode b IIO! 11111':11 In !IlklillOn. the capac:·
,tanC" I, 'cmpcr~run· dependent. flj;un· 5.6 ,Jill'" Ill" ',me dd~) w;ncrstrd b) a "mea))
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,-I , I· , . , ". A .. ,..,fc---; -~.- - --/ .-.
L~" .... .. • • • -•• -.... 1 .. , .
-- l , .. ." _ ...... :
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• - •• --- • .-.
., ' L ' .. • ~ • • • '.
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d.CJd.;. M V I llJ. I 2 nF cap3~nor and I 41 n ~''iIOf. 0' rr " rang~ of .ol[J!I~ ih31 is appl ifil
a"f~ 1M ,'ancap dlO<k (57).
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The progrnmm:oblr d,gnal de lay line-. OS 1 020 """t. [1, 8). "I~ chot.;:n 10 "'pl:o.:e ,~ ~"'r·
.cap dIode delay StNctun:. The OS I O~O r.ene~ Ij an 8·1111 prn@'QffiIllablc delay l i~ . "'1m
delay Sl(p sIze as small b 0.1! M. 10 3.;ki,hDn, 11 alln"')' an ol-'"no bet'" ~eo prn~ming
on liS 'il'n31 p!>rt or paIlIJlel pon. The 0 51020·015 {0,15 II> S1.:-p siu) was cho;,:n for
the applICation. 115 ,I pro\"Kk.:IIl eff~,i\~ ssmphog lRquency of 6.67 Crllz for the UWB
f'I."(CI '<'1 Th~ samplmg fmJUmcy b 5Ii~hll)' hl~hcr thL,! W mlrumum samph .. '!g I\:qul""
menl cllkul~lc-d in Sectiun j 1.1 . A fll\'T·~~p-!>izr deby hllf' IS commercially a.-allauk
f .... 1II F l .. "I~h the !>lcp-.ilC:<S .mall as 50 ps , rOI 16050) HO\I."t"""'. w co~t oithlS com·
pUllen! I. much h'.:her than OS 1020 ~ric:. \rOH6050c<.O:lts appro~ im':I!~ly SIJO. "'~"'u
OS I 0:0-01 ~ ':O~I> 54 ~), tho."ro::fulc .. POH60~O '> nOl ch<r..cn for Ilu. PTojccl.
With OS 1020..(11 S deilY liM. I (Olal of 155 del"y steps u al lo",-N. h~. ibr ml.~lmllm
TI1nl" of OCte.:" o!: .. 'Pf'1\I~lrnaH:ly 5.76 m A serooo IklilY lillC'. OS I O~O-050 (O. 5 II!i Slep
.'lC) call he u..cd '0 "'''~s wIt h lhe OS I 0~0·015 10 pro,ilk ~ long.,. ",n~ profilr. 110'0'·
cV~I. ") ;ncrea' ;ng III<" ItI'ill h Oflho nngc: proW,,- ,( d"";"J"" 11K- m3A imum pruliling f31r
of ti>e 'y~ l em, Furthcnnl1/c, e>l~h dd9)' lme prod"""" '''''<'' dc: lay ",,,II • CM1a;n IIn ,allOn
Tllrre: fore, 'f tv.·o dolay hnes wcre: used. cahlmlU(H' is reqUITW. fM de-1>lY .. me ahgnmc:n,
CBhbr.lt illn h ~§cd 10 tn~ Ih31 IDe wmbmN dd a}' lmw l§ UlCleascd IlnMol mlulD~
or rcpc~1 ~ ""tay . ICp To Ikmonmatc Ihal using prognmmable delay lin r improvrs the
rad>l l .[lbll'l~ and oc~urncY. "'hen nnr.i-"'",d IV th~ "aneap dioo:k <kl~y 1me. 11 ""as de·
~,ded Ihm 110r " ,,<:: OT\(; dela) lin ... OS 1 O:O-(lt5 .... ill be ~uffi"i,""t. .. 11 mel the "''lu,reme:ll
fi~u rc: 5.9 Micro':<ln(rolicr ~mo OOard:wl the progmmnl4ble Jd~., "",Jule
Ahh(l;jgh lho: rrsisLOr iIlT:I~ Inside the DS·IU20 i~ Ia.~ Iflmmrd 1<1 n"l1ch the .:k~lgllI:d
, alues. \hrrc will Jli ll be ~ '1I(.3hOO of~ gel"lCnl1~ <k"'~. IIAle rnlAl the " Clmln .• 1 old")
time. i~. (hI' dela~ progrumlOCd inhltlle del.!.~ I'nc. A !tel Clrm(:a<ucen>tnt~ .... erc dor1e
lI)in~ un al·eurat~ di~iu!l oscilloscope (A~lkol lolinium S4~JJ,' 0)-,0, '" eha".'lt." t the
ub...,r. ~d (mu~IJt\'d ) o:kl~} :lS ~ funclloo of \h~ progf"~mmcd (01ll".",, 11 dclu) H&urc:.5.10
hod riwun: 5. 11 wmpar~s thl' mnsul\.-d xcumUlated <klay .... Ith nnmlllal accum"Med
dcl(l~ ((If DS I 02(}'{) 15 and DS I 020-050 I\:splXti' eI) .
. ~
,.,. '.".,01.., ..... -H ..... ~t " .. ...
• -" .. • .. - ,
The 'kl~y time was mtJsurrd "tlh Ih • .' DSO"~ tll1iling the linK' d,t1Ct'-<!nc<! beh'C("n the
input ~nd ~'u(put <.>f Ih<." Jcla~ linc. The a, ' erag~d lime difference i~ ob .... ncJ U~IAg tht
J\'~raginG funct.on ... " Ihe D~O. O\~I 2.00D.()()() pul>t"s. .~ is ilI1 milibl deb} of LU ns
li)r toch .~rlhedda, ebncnl. "I"ch I ~ (1\11 ,htl"" in J"i~UI\: S.IO anil Figure 5.11. The
,.,
." >U" •
••• , , , ••• " II·.,.., "'" ..... . , ••• IMa ... ~' , ..... ~ • " "." ..
. "" ' '. • .. '/ •• " ,.. AI .'_ '" ~ .. ~ •• I~ •• '., ~ ~
e.n ... I ....... <"",w.o',,'"
Fig"n.· S.I I: IXb) tim~ V.5. rro~rnl'11rned ~\"k lor DS I O~0-(I50 r J I·
m .. ' ;lsun:d delu) IS ~IULi,' d) cl~ 10 lho, nomin~1 dda} ,~Iue. "ilh" tonstan! ern'!" in
ca~h ~!CP. ~jnc ... lhe slop\: ('filII: graph ~ho" n in t igun: 5, 10 is (Airl) 5lnooW. it ~ugg~s ls
lh~t neh dda) ~ICp si~~ 1\ (on~lant. 'h.' linto: dclQ~' n:pre><:nlll>c sampl ing point.> on the
""urn C<: no.:s. Il el1ee, tl>c COI"ISHlnt dclo) s!cp si.:c ~nsu",s the relum ,-.:oo.es an unifQfTT1l)
,,~mplcd Ho\\ ner. >Inee IK:lunllklu) >lCP Sill' is slight l) Inrgn-lilan 0.5 'IS (Ihe slop-.: i>
>TIXI'Cf). if '\lla;e~l' Ihol Ihe ,alllplillg freq~I\C) ~1 ' Shll) lo\\el li1Jn 6.67 GHL
n,.: tn&!,:.el ~~I\CTal(~ '~I\:>p..~l<it>lc for '\\,I"hillg .~\ the ,.1I11r 1cr module fOf a short ..Ill-
1"31100 (IH"clili) ~ 11"1. "hkh dctuoo the ,ample '"indm'" TIi<' II1PUI of 11K- triucr
!:Cf\CT"alf}["i~~ ddo)C1l 'QUill ... "alc. ln "hK:h lhe: lime dda) i>sn b~ 11K- dcla~ hili: mod
ul .... Figure 3.12 ,lIuW:JIc51iw;, bas~ <lJlt'r;\hon ('of.1\c ~ltmpl['f module: . Sampln arc: L:I~~n
!II di.«:rcte limes T .... T ij. T < ell". A~ iII"W"~I ''<I in Fig"'~ ~ I::. Ih .. ,,,ildlCd-on lIme o r
lho.- sarnplCT" module \i. ... . Ihe sample ." ;n,Io,,', no. ... oJ,." bo: .igJu r.~,\o'I'} <;m:tlltt Ihan II",
pul!>C "id,h 1,(,1", '"""miu,"" >,gnal ",oJ ,h .. 1k:1.~ "~i' ."e {II I~ n<1. Ill!, L~.n CTl.<.Ure
Ihal. "lw:n the: dd3~ i. '1<..' Iv T .... lho ~m"k:ol ~igo131 al T ... ",ilt.:;1S lho.- !lUI: r('tum ""ho al
T .... lII1J ,,"I lhe: •• el'3\:t"d "go,at • II lhe: ""Ium "'l:Il.', I'ocl" IX:! I .. and Tn.
~ Igurc.\ 13 ~hnv.s the ... ,I1:\l1l for me, lnwr g~IlCT"aI"'" lhi~ eircuil is simi llir tv tiIC ci""\lil
des.gn used for m .. U\\ 0 pul5(' g(~r;olOr l"hc pulJ,e ~cnCT';\lcd b) Ilk: 1ro""SIIH i5 uSNIt(>
5" ilch the- samplCT" module
I;;!ur~ ~ 12:
,
r" ~~er oel . . . .. Iccal", e",,'lu!
the d ,<,Chargong lime far ClIo reilO:h rn( I\I:'W 1M, "N.'f<.' I ,IoU I:" II = '1 ) + -I 5 I \. i~
""""~r Ihan :J;,. twll '", ' !" igur<' 5. 13 iUUS\rnl~ ~ Ihii oper.uior .
N o , , , & • • >
, , , \ • ,
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T"".
"ho;r~ i',_,,,,, ir 1;5 Ihe \'ohllge 3Cr055I~ c.1p3C.wr, 1',, (1 _ II I is t ile ;n illal ~,, 1I3!'l acr""s
11,,- ~nl,.....,il()l ~nd H( ' j, Ii>e dliCh.:lrg,mg time rOO,l.l/ll T,~,<"" .. "OC. Wllm I r7 is dC'O,:r~aSC"l
h~ a l w Ihe lillie" Ill", fur Ihe car:ICitor \0 di$("~ lOll\( n .... , u llK can ~ rJI(ulalrd
~ . rulI,"",nl! '
I rom abo,,, <'<IIIali ...... II ,ho" ~ that lhe t"",· ""lUll"" lill" ("21 II) <li...:l\nrl!e IV 0 Be\\ 1:l1u.: is
rdal~-.J IU I ..... r~I '" bt.·I,,·rCfl.11 ;~. the chan!l~ In rL'Cc;,«,I " ' II~He, and 1 ., .J = ' I). the initial
' ull:l~ ",'r..,<s ("11 . lie""" 11'1<:", ;, no fiud di,;..: h:ltl>f tIme Ihal can be ~ :;c,d to dcs>:rihe
Ihl' pa» ,,( d,-.eh:lrgin;: lime in the caSt' "f 6' '." Q. N~I<'nh<le s\" from r;gur~ ~ , 13, il is
.; kAr Ihal Ih ... d,<,el\;u'l!inl> I"n<, fot Q I IS le5$ Ihan Ihe pass il'" di ~har~in): I imc.
~imulallon $ "cre ~ooe uSIng r<.IKro..('ap 1-1811<) ~ .. nr"m Ih," ~k"", cxrl.n.III,,,, r;~.
"r.: 5 16 St.Jwi I"" inl l·.<;r~lur rireuil di,,~ram IhaL i, u<.cd ,n 111.: , ''''llbl;'''t the 1"'88<'1
pul~e ii rt'P<'~"" "II'd b~ II,,' pl"'" ~""cr"l'\(" \ ' 1. Ih~ 'ol,,~ 1<" lhe re~iS lnn;, tap:lCllnrs
and lriJ.;);ni,,~ pili",' widlh aI',' s.; " bl 1"1'' '''' Ih~ ocLual ,alu~ Ihal.lle u,cd in the hard"are.
lIuc I,. Ih~ "",iMin" "r,lo" ,i ,,,ulal,,r. ~I£ure 5 17 s/m"s In.. s.mui3hon 1'('(,11 " . Ill.: rt'd
"""d""" "'1",'e~111 lhe V2, th~ r«ej\·e'(j "igrot. JIId b!~ \\J'eform i~ the \ ol t.lg~ JI I1Qtk
11. 6· 11 ~ ~,Id ,",,>de 11..,.11. ... The simu lalcd resu lts H';(\ II!(> aoo.e <.'xpl3NIion {Ion .he cir.:uil
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/
". "~!tterr t s,- pr.or
~ln.' ~II
~iltun .. ~. 17: fl1c >lmul~!<:J ... "l pIOI "J<..-funn Itl (' j nod.: R6·RII \bl R7·R9,:m.:I V~, using ~imu IJIIOft c.reuil >tI_ n 111 fi¥W\: S. I "
Sin~c Ill.: aCli<~ chargll1l1 lim.: i~ I<,'~ thall Ih,· IIas.;<e dl"""B(lting time_ hy n:;ct_;n~ tit.:
In(cllra! in@capJrjIDrC:1 Jnd L 2~. 111<.' !kllll llkr IlIoouk \\ ill al\\'PYs Utl<k~o a."l .. ·c .. ha~·
log process for !xllh COlldil ;,111 Ill" .'\r" 1 hi. ,,(nixl j. dy ,hnncn;ng th<: • di",'h~IXC' til'Ilt:
r<'quired lor ell I!) reM!> Ih~ ne" I " ",hell ,'\1 ., I, ..... gal;.c. Anal"" "",it"h AD(i6(l 1
i. ch"sen for llus II!lphCJ II"n. I hr 1"0 aIl81,,\: ."';Ieh,:, Ill>: 1'1"",("(1 acr,,>~ ("21 an<! C:!1.
\\ tlcn 1he dclay Ime shdesl(l~ I"''' ~~Iuc. lhe Ull.lit)g ." ,Ieh ",;11 he hlll",d nn by Ihe mI'
rlVCunlro ll~T, :In.J lh~ cap3cl illf .... Ii I he di",harg,'tl Ih,(Jugh the nn.r't",i,t~ncc "f Ihe ,m ~J,,~
' " ilCh. ADG60 I is ~ dua l su pply, 2 !l on,rcsisl:uK~ anJlol!. ..... nch [ I ~I. fk ncc Ih~ rc~
1;111\' ,,·q~Ir."<1 h' diKI\;'J)I" the "ap;lCilur IhrouJ:!h!l1e analog 5witch. is d('I~rminN h.1 Ih,'
I,me [",Nanl r ......... f ' .. R .... ~" ... ","11 - ]n,.
R. ,e,if> the n:!of'1 :lCl iOll. Ihal u5ing anJlog §" ilch "ill mridl y ,h '>Char!!c the "1l<'gllll'
"'i! <-:.p: .. ,ih'fS. t.~"'Timc01S an: Cllnducled by ronneclmg the lr.:an=in,'r di,~c tl ) 10 Ihe
=~iH'" 'l~ ~ "'~.,,"I ,;;tblc "no.! ,l,Iil~ b)~ HllcnU~lon and aC'Iuirin~ lbe s:lnlpkd r.:f~L\'\-d
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rj~ 5,18: The l ... n).;1"lt~.,j "'.'·crurm Ihall_' :.ar~'lo:d"~ !I1~ ,,,,,,,,,,,e ..... nh (a l "" r<:SeJ It> I " ,,.,,1 (",.eIM-,n. u,,"t Ik a,\a1oa ~ '" ,:ches. UlCO lDlcgr.mon urn.: IS 12~O Il s.
.,
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,., "' I~'mu\...,.., n .. ,.,,,,,,,
~'~l f .• f---,I~"
"T ~ 1!:-----;-.
• " " " •
F'Ji]lIrI: ~ ,OJ' The lfal)jllllll~ll "l<\'dt)nn III ", I. sampleJ b~ ti'l(" =civ~r wr.h l al no I'net Ib) n.~ li,lII~nun. \lSIIl$ rhe analog $WIlC"~S. ,,,~ mt~l!"':"'" Iime-" I ~5 1"
w"~..ron~ hgun' 5.1~ ,110'" tllr ..,1111,kd ,*B'''·!')nn ",h~~, the' "neg .... !i " .. t,mt I, ~~I
\0 125U .ii~ • .. c. Ih~ ,\clay hne ~Ihlc' t(llhc 11 C\! 'alue c,·try 1250 II' Th,~ "n~'gtat"lltt
11m,· " d>O'(TI. S<.'! lha: lh~ micgn.!U!¥ ear-'lC,1(.t ... d I r.h~r¥~,1 t,. a iXILOl ... ·h~'" lIlore ,",111,
pktl ~'llnal "ill OOt "'<'rea .... !he ch'lI",1 '(tl!~g~ Jouy lunher H~n~c. tilll.n::; I ~ &I,o" ~
the 'In",' n.'Ceiv~d "a"efomo I" Ihi~ ""llCmll'I"I . Ilw J..IIml'kd " .. ,,~l"",· Ii:"-]:'oth ca,.c~
t wllh ,,·dtoul n:>e: fullCuoo) arc "nually ul"''''''111 • b thi.'). wooid I>C'
FIlI:ure S.19 .hvw. the s:ompkd 'u~"r.,"n "h('" Iht UUcgDh"1! tn"e " J;et :" 1 ~5 us
r rum F,~'UIT ~. :C/I' HJ . " >h<:M ~ 11 .. 1 Ihe 1 1o~ ,,",cgrahng "lIp;ICUN' i~ ,"" cloa'll~l ,u Jhc,c"tl~
10 Iho: tCCct'-cd M);IJ.1\ "hen the "~Hlonn ch"HQ ""1',.11> 'I' the n,,~al"c ,hM;:hOn I' e
.:lol ~ . <' 01. Thc nC\\ -ampler " 'nll rc<;ct funclHloI I',oou.;:e; I lfurt ~ l<IIbl ..... h..:h r~mbl~
lh~ ",mpk.! ".,c(.'nn ,II f 'K'''c _~_IKlh). 'nWl~ It.c new »mplcf ... ·uh I\':~ function wIll
~110" much ra;ler flmg" prolihng lhal' the nr~in31 circuit h' practice. ,un /1' dwell flme
was u~d per .:l"
5.4 !lost-amplificr module
Tile pos!'3n,phfi~r mvduio: n"'l.i,,~ ),,(, ~1.gc:o; "I ""'I,l i/,eal'''!\: mMrumCf11JIlOn amrh·
fier AD620 ai,d uper.'''on ,,,"phfier 11 (~~ .
-- • , • "d~' • , .. .,. • • • • •
R(O t.2. R, < • • " • 0 • ,
" -I · , • - ' - \'s .. -• , --. .. • • • L....!!. ,- oro; +/ OUTPUT - -----,!' • -- • • • :-. • " • ". AQ620 '" •• -b .. , .". • • TOP _"EW
", , ..
I'll<: I\>, 0 bra.'\Chci of sam"l~ modu k. th,' mtcgMlllll "~rnplcr ""d the re ferellcc \.an, "Ier.
:lCC connected \0 II'" and ·1 t-. pm. uf Ihe !r_!o1ft.m!Cn!.'I,(~, wnpi 'her A I )6~(). "he,." th~
\'oita£c diffen:n,e bct\\"~,'n IhI" I\lV I'ln< b un'phhcd An,! rl:Cli~~d 1" aropo::ar as a IX' othe!
alt hc VU lpu! Figure 5.~n $I\('M' 'he ~i"'p hhcJ drewl diaSl1l1n ~nd the ronncc,lOn block
di~!>,.,.m f0l" A I ~~() w hkh i, reprodnceJ Tm", I I :1. A I"" pan n Iler SU\lClUIT 'S rcqui red
to place'" l .... nl of ~IN and ·1 t.: pm to numm,ze the Rr intcrferencf frum bein~ ampl ified_
ri9-UIT ~ ';'1 iho\\'~ the lin:llil dia"nun ror :10(-["" 111l .. 1i Iler. "h,ch " ""U~I h) I (2). Th"
fi Ilcr cul ..... rr rrc'lucnc~' ;.> ,kl~nn;ncd h~
",hc~ lhe value for en needs 10 be: at ka>t I() I!m~~ 1aI}!~T Ilwn (.(.- . (,\ en""C !ha! rhc
C<lmmCln-mMC rcjec:ion p<:rionnane~ rhat is oc~iJ!OCd for AD620 lS "ot dimin"hcJ [ I ~ J Smce the deta) tine i~ slid a< rate of 500 j)' P'" 51CI'. Ihl' mimm"rn cul .... '/l· tTcqlOcncy nf
Ihe 10" pass fi ller i~ 2 KI [Z . The eut--orf frcqucnc~ of th<.: I"", pa" .' f,ller i, .~I Il' 23 ~ HI.
Th, s allow. a ehoic~ of faICtcr sweeping rale 1<.' b~ u,.,d for fut"", d~"\'dopmcTlI TIlt: <"'01-
r-::oncnt value u.<cd in the f,hn arc R = lSOHl. C L> = n rF "flU C{ .", I.~ pF ,
" , ., .<>.0620
riSUI'l' S.21: Circuit diagram for filtering Rr signal [ ]1J.
Tho; ~ain 1)( ..... Dt>20 is <ktemlincd by rat ii' ,'fthe internal ~ain n:si~to .. il.1d RG. whecc Rt.
" the extl."mal n:,bloT nmncctcd bI.-rn·ccn Ihc IW1) R(, pin •. The Gain (,f Ihe amplifier is
C'alcuiHl.-d by '
G 49.4Hl
- +1 "
Flgu:-c 5.22 .110'1'.,,5 the gam v.!. frequency grDflh for AlXl20, In th,s IheSI'. the ga", of
A 062u IS >el to 16. F 19ure 5,23 ,ho\\1; the ~trCuti d,ag.:lIll for the post-a.11 phf,er modu:e,
TL0'l2 (1..I9AllS u",d rUT lcwl ,h;ft 'n~ and adju~t;ng Ih~ ~' gnHI amphrud~ ocfore Ihc
,ampkd ".\lnal i, Ji~it'Lcd b) th~ ,' .. DC As th" l1ll'Ul rang~ 10 t~ ADC is limIted b<.'1wccn
o 4"d 5 V. Th" ,"'lput SlgIlH1 of Ih~ AD620 :",cd~ 1<.) bI., I ~vd ,hlned I~' 1 5 V Thl' IP,n l,f
TJ o'n I.' adjll.<;l.d b)' mrn,,,c tne rotc.m'alllCICt R 16.
5.5 Front- End Amp lifier
A ·tr('ln\_cnd· aml'1i!icr is requin:J 10 amplify the n:tum si~"31 bd"", the .'IIImpling pro
ee,,-' . rhm"~h pcc-a'''l'litkalloll. tile overall S'JR of !I1~ 'Hmrkd ;igm,1 '" ""rca.'~,J.
'<" ---:-:= ---
-f ,. __ ~==~ S ,
" .,
Figure ~. 11: Gai n ".S frI."Iurn<:y).:mph ror AD6.'O I I ~J
whIch InCreaSe., Ihe cnance of detecting a weak !argCl Il'>PQJI>e. Funhcrmme. Ihe amplr_
hed ~ignal i, Ie,; susaplible 10 lne n.OI>" and diMonion from lhe Imer ;';;l1npling =ge,.
h" Ihe llWB 'y;!em. lh~ fmnl-end amplifIer nee,b to ~ low noi~ and haye a nat "ai"
le~p"n,c "ver a large handwldth
0"li-39-;- from M,m..( ·,,\:ulI, wa~ cOO-;c" for ,hi , applicall<lIl. 01.\ it ()po:rJlC; from DC 10
70H£. ,,; Ii1 19.7 tlB g~i(l at] GH7. Gali_W .. ha<;a I",,, nni~ flgurenf2 4 dB (llOi~lem
J'Cn1\ lIf~ of214 kd,·in.) m 2 GHl.. ,,-n idl " luwcnhM the ",,'m 1lO1~ of amund 2'XJ kelvi n.
Figu", 5.2 ~ ,1>.,,,, 1~ ~OISl' li~I""I' anJ gai" "fllle amplifier o,er Ihe "peranng frequen-
.-.... ~ , , . ~-=--.. ,- -.. "-, I
• • • _ .. 1_) ("'n
Figure 5.2';: Gl1!ph ~ho" ~ fa) gain. (bJ noi~ fi~ure over the o~"'tiJl~ fr~quen.y [ 151.
Figure 5.~5 show th~ connection for Gali-J9+ amplifier. GaJi-~9'" is deslgn~d to opml.le
a~ 3.5 V with 35 rnA. for a optimal perfonn~"". uf high gain and mode"'ldy low 00,>".
Th .. efore. rnbtor.; ar~ required fOI biasing the IS V supply 10 3.5 V The bla5mg l'I:,i5-
lHller neWo<.! is approximately '~ (,N '" 3400. The pown di~~iJXIted in Lhe biils rcsi,lolS
b appro~imatdy O.J'" w. H~nce lWO 0.~5 ~- I'I:SiSlOrs. 160 Q and 180 Q . arc used in Ie ·
ri~~ \0 0' c,,:ome the PQwrr dis,ipatiQn limit. The .1<,( l"Uuplinll capa("itors.14 nF [14J. arc
placed at II><: ;npOl and oulpul of the amplifi~r. which are u:;cd 10 bhICk the DC' componenl
from ~~tcrin.l' the de,-icc. A b,J,in!( ,hoke mductor is required to place oc:wccn Lhe OUIj'IUI
(lr Ihe Hmplifkr Mnd the bia~ rni>lor. to prryent th~ RF li ~nal from lmcrferin!; wllh the
SIIWll' !>Cure< [13J. The inductor u~ed III r-i~'I.Ire 5.25 tS a 6~ nH from (oilcr~ft Ob03CS
~ ~ri", . The m"",ured inductana al 1.7 GH<: i5 ilpprTl,imatdy 168 nH f9l-
Fi~ure 5.16 ,no", II><- rrolll..,nd amplifiertcst board. Five \ ia~ are placed around tile am
pli ~e(' 1(1 Wnntti II,,: I"P and bo.,Uom ~n'ur.d pl."., wh ich Cn,urr) the R F .;igna 1 ""UU 1.1 be
prnpelty gOlde<;l '0 ,,,,d oul of the d~,',,"c [11]. Fr~lIre 5.27 ,how, Ihe "Htplll wavd"",, uj
the amplifier "hen a -JO dBm 5inll",i<iat <ig.nal . al 1 GI1~. is ill]1l'\ 1., the amptilicl. The
sinU50,dal signal is generated by Agilcol i:4400B SIgnal gen~ralor Th~ - to dllm s l~nal IS
m~a.\ured on tl>e DSO. w;,h the inpul impedance of the DSO .l eI In ~O n The mca>un.-d
61
, ,
r igur~ 5.25 , FrvnH;n,j '''"1'1 ilier ~"",,,,,.( "'" cirellil ,jiallra,n.
pcJk·t('·f'Ca~ HlIIH~'t' i'I'f'f"u," lIUtt<'i) '-1 7 mV. The utll"", .jgrul. ~~n m hJ1-IIr" :t;?7. i~ 81'1W(',jm~lcly 167 \ Ikoc ... Ihe ~am "r lOC arnphlkf. "I 1 GHL i~ af'rrU~mlalc1~
~ 1. 1 dH. 1111' ~jlfw, I' ill! 1110: r.. ... " .. ,ho""" in Ii);""," , 20U _I In . I>i< I"""~. "'" (uh· I~'"
arc ca~lkl"" 1,' ron" ,J.: ~ O ,j 1\ ;;;"'" II I S ( .1 II
I i!!ure ~.27 Sigll.ll m~lI.;;ur~J at til.. (\!J\(1tl1 offiali·J9+ A I (,HI s.inusoidal ;s injt.:\ imo lh~ amplitlcr W " it~1 ",ak. ~IMI In V'dn (,,;11. {I V "lI""n Ilorizonlal.'li.":31~, I nr..'dj,
C hapter 6
Simulation
Sunuiallnll nf The UVVR "fr.~ all,J (il<; ,mall" rmm~!;on al~llrithm5 WI;'TC ,mp1cmcllI Il.~rng
1»11\..'0 In Ihl~ charter. Ill(" rein It r,vm ~ach 'tall~ or "J1ll~1 pr~'S lllg w,1I b.: prcs.cnlcd.
~In~ny. a ,lmu]aTlOn 01 1!lliI~ml' mllh,pk laJ)l:cl> wil l be f'Crfurm(d.
In., Lr .. n.<.minC't! "gnai i ~ '''nutate<! u)inK the (,,,,,, ,1en~~lhr uf a GHus~iJn pulse (49J.
"Inch I~ exprc!..<ed "-,
.. hel'\: r ,. rhe I'ul"" ""It" ano.l ~ j,. ampli tude ~Ilhn~ f~lor. Jnl/K ~ LmuI3ti"'·I. the pu],,,
.. "dill I~ -ell" r =0 5n~3"" 4 = I The 3 dll band ... ·!d'h uf Lllt' r.ul.c 1.1 3ppro_um~:el}
8 - ~ ,,!I,ch "C<I'''''~lcnllu ~ CHz FI~ure 6 J ~.~ the .. mulalcd ~ulse m urn" domain
and ffcq"CDC~ <lowalD.
------'''''' ... "'".,-"'"''.,-~-''''--'".,,-'-'-----, ,
...
" ,.
,
...." ... :~ ................ ".0-...
,
,. 'h i I «qoIffI<)' cI""u. n
111 ("hap'e' 1. the "'pt:,unc"" w~re ,,'lIlduct(>.l ,,>jn~ , ...... 00" -1l~ ."Ienn.>.. ,,;hi(:h up.. .... tc
bcl\1o~ I 1<~ ~ (,H7_ In i'lder Hl .irnulale the rc.1 'et:e"L~t rllllu. tbe "lnul ... .cd silP'al is
band-ltmncd HI I GH1 ! I~.,.cncy conlponenl fTOm 1 (,l-b '" ~ (iH,). Fut1hcrmurc-. m!))!
r>flk sy~lcm rafamcI~rs us,,,! In Ih,s SImulallon ar c,~ same as Ik r.:al S>~lem hanlware
cond,uon.
• CcnlTl: trequcocy f, = I ~GH~
• Sampling frcq.,cnc} J, = 24(iH,. ' ·'gun: 61 SI"K"M"t.,NI an .mf>Uisc "'·lIh plll~e
"",dIll .. \).~ ns ha .. freq uency comp<mc",~ IIp 10 () (,H,. Il rocc. a >.amphng f.c·
qucocy of ~4 (j ll~ ,~ requIred 10 ~amplc the hlgh C"S1 frCo:j ucnoy component of w Im pulse In tile real sy~lem. 111(· reccil' t'd s'~041' ; band);mlloo b)· the ilIlleMas Ihlt
"' C1"I.' used 10 trans mll :and receive the ' igoal. bcfon: II 15 sampled by the tc<:e,,·cr
Hem:.· Blown 5<lmplin~ f.cqumcy (:>, 6.67 (iH ~1 is sufficienl.
• Nl,lmbcr or recd,·in~ elements N 8.
6.1 Effcct ofSign:11 P.-occssing
F' l!Ufe f, ~ ,""", Ihe J"'Ul"""" .,r,he ... ~mdll~cr elC111cnB ~ml II><: laJ1',CI .\ ~ingk la J1',e1 jJ
pl:ao"d III m a", ... y fr",,, Ihe r.>dar r 'l!"I"C 1> .• 1 '1\" .... 5 the Inm,n1lllcd anJ =·clwd W~,·cfUfm
fn. the fi rst ~i'mg elcm~nI in I~ arnoy. Ihl'" ,""c",,·ed .illnal " t lInll' dela) \er~'''" of
the 1T.U\Smmcd signal. IhI: lImc delay for each .ccclled sIgnal ,.I cqu,,·alcnllO the lime
r:"ql:.lr.!d fot the Iran';IlllUed ~,gnal to reach the IOtgel and rclUm HI Ihe r""c'~,"g clemenl.
The amphtude- of IhI: =t'vcd sIgnal ,s comprn.~lcd with ,~ algorithm. Thcreforc. Ill<:
rec~lI·cd Slgfl3. has same amphrudc u the transnuncd si[!11al.
S'gJlK. """"".;nl:- 1I~,"j,' .·i!lw.-r ~ rn a'cb"d fihr art..l lUI inv<"rSc fi llcr. is pcrform~d on the
~e"cd sip!al Aoth lilter Sli pI'm;.,. 11M:- oul-oH .. i11J 'I<)i.e IOld buolil the ""hand ~lh'ml .
", bieh imprmcs !-iNti. . It", magnililde MIlle FFl""s ofhorrlh filler<; are .hown in Fig"'c 6 4
TIle rrT of the m31CiIcd fihcr tS thc COIIJIlg31C £If the H r ofthc lran~mll "a.-dorm. and
the FFT oflhc '"'~~ filtcr is the illl'enie ofltlC rn of the II1InSmlUcd w~vcform. S'llCe
Ih,· ;n,c", IiIt' T 15 on ly ,kfinru OJHT ~ ba"d"idth (rcfL"T 10 Sccllon 3.4 2). a 1""('("' fun,tion
..
..
..
,
• " ,
,l..--,,---------;,---------,,--------__ .c---------,.---~ .........
,---------'."' .• -.., ....... , .. .. .. .. ..
·c ..
Fi~ure 6 3: TnIJ1>milted and 1\."C~iv~d "llvdorm .
..
..
..
.. c, ..
c, --I" ~tmh!l.HIT .. Ibl In.rn.o: fille r
1 I
Figure 6.4: The magnilud~{)flho: FrT of the (a) matched filler and (hl i",~r<~ filte r
"Ilb bandwldlb uf I GHz (frl'qllcncy tomponcl1l from I GII~ IU 2 GH~). I, u5nllu band
limnallht fr:quo:m:y s~m of thl' signa l.
Flgur~ 6.5 and Figure 6.6 IhOl' the aoolyu. rep"~~nlalion oflhe Iht m"lch~d liilcI':J and
;m er~ f,lleral ~i8nal ~peCl;,elr
Any l-e~1 <lgn~1 ha.~ a IYI" .. ·~lde ~'(Ju"e, Iran,fnrm Ihal are In symmetry A rcal Signal X(I'
h&. k <pe~lrum "h= r ;. -J) - X'fl) (22J The anal)~IC "r=enla"n" "fa real ~'gnll
..-11' I, definal 11., havlOlI: , ..... 1)' Iho: pnsil" e f...-que",) comr""lCnl~ [22 J-
X 11' _ {2x,.n .... 1jI~·v I
o I=:.O /<0
...... _._'n ........ ____ .,....,
-" " .. .. -.
,
': , , .. ,,',
FigU1"C' 6.5: Tne m~dop Urlhe mawhed filtered ~ignal.
-.. ~~ ,--~ ... ,-~-~- •. ~ ---. , ,
'" " . .. " . . ", .. ::. ~_' ="'l') I"" '"",""-r--~ ., " , , - _ ..
"
,
The "'.gn;lu,," " r the r~ucnc) 'ree' rum "f (he in, e~c Ii hera! M~,"I ( fro'" _ I'u;nl lar·
g~; ) 's 11. r"<'Cf fUncllOn_ Hence. III lime dm"ain. Ih,_, i, Iram;fn.med ,<'0 D ""I- lunch",l ,
Th~ h,gh wJ.:-I"I>e' ,)Ih':r\'~d rr.:.m FiJ!",e 6,6(a) ~~" I>e rcrluccd hy rnh~ri,,~ Ih,' r",
'luency 'f>eClnH" "flht in\'~"'" lihere<l "J!n"ll~21. A " ,indo" l'u[l<;(,,,,,, ,,,~h ~~ Harmmg
.... ",J" .... ~"d Blm:krnan ",,,,dOY<, can he u-ell r"r (h" purpo-.c The ""u\( " ,hu .... " in
hgurc e 7, C OmpHnn); W hgure o.t>f a). Ihe "lk·lvhe, m Fi);un.: 6, 7(~) 311.' 'i~nilkanll;'
",due,d.
"~. ~J "_ "' " ~ ........ ,_._._,",_,
--,-
• "I .. "
,-
.~ '~-~-.-,,---,-r-,'.-', __ _ .. ~ ;.' •
\Ol Tu",,, tLlnlIIO
rho ",",ell'll] clJrnp<",eTlI, or 'he f,hcrcrl ,io.'lla l i, Ih.'1' h;o"'ba"tktl hy mu l liplyinll'''~
,i~J w,th I! :!./~ ill (h,' tin .... tlom/lln [n] Fi~urc 6.8 ,h"ws lh~ b<Lwha"tlctl ,igoal
after u:;ing mal cl1cd fillcrin;: and in-er . ...., lih~ri"); . Thc ccntre frcquclKy I S cho,cn as.
.rc = 15 Gllz. Unlikt·t hc in-c= fllt~red ,ign~1. t h~ mJlehetl filtered ~ignal i~ n<J1 b~n ·
dlimitcd. lienee. the ooocbandcd malched fi itcr,-.j signal ha~ 3 \wo·side fourier IrIU\~form
Iha, arc not ~ymmetrical. ThcreafL:r. Ih~ h<:-Jmforming ~I;:on\hm. which;' ck>erilxd in
Secuon 3.·'.3. i , applied on Ih~ ba>ebandcd 'igna\ (for bo-.Jlh ma(d~-d filtered and inv~r:;.~
filtered l igna l) 10 produc...- :In im~g~ "hkh I'\.',·cab \~e range antl angul~r po,ilion of the
tRrt,:rl fi~urc 6.9 >,h"w, (he oo.m(ctrmed ,ma~e In lhc ~a,c 0rma(dl~d f,hcrin~ amI ;n
,'cr,,: Ii hering. "II kh i, arp l ied I" The range pnlfi I.,. n:'I"'C1Iv~\y
rhe bcarnfomlM ,mages "II;cf"l'Cd lfl Figure /),91l.a\"C IJrg~ ~ld~ ·lob<:s In (he azimuth d,
n.'Ct ,OD. Th~ "dc-Iobes can be reduced b\' 3pplym~ a H annm~ apcnlJre \l':iJ!hung 10 each
of tl!.: 1\."C~lving ~kmml5 wher. ~ummin~ the- ,ign;.I , for a foclJ;cd pcin!. Figure b.IO
,h",,:; lhe beam r"rmed ;mag:~ uf lh~ ill\ rl"><' f,hretl (" i~h llanmng .. Irx!",,] rMlg" pro
fik,. "ilh ~ H,,,ming a[X"rtu"" ""lghlmg appl ,ed. In gctlcmL the >ld~-I\lhn ar~ ",tlulA·d
Ihroo)!;h "Hid,,,, limc!>ofl.' 'n "''';:~ an.d 117imulh rlor~c'iOlI However, Ihe main-Iohc h
""knM 11\ Th ~ pr<lU''' F.gure /) I()(h) " th., ""amtoml~d image d''PI"y '" a fan·ru,am
f"'m~""" Th, .. " nhl~IIlM 10,: m"Pl'mg 'he ,"",,,It fmm rirm~ (, I(~~i ,n", ('an,.,i;,n co
ordmJI~'.
\',~~.,--~",-~--c: -......-. -_.,
~''''''''''' ''' .. -< ... ", ... ~~ ...... . . • .-..
• •
.. . ' ... ._-
Figllfc 6 , ~- The ma~JlI (uJc uflhe b",cbHmlnl ,iBn. 1. aner \"1 mHl<'bcd r.hcnn~ (b) in~er!;C rlltering with applica110n ofrect "'00""_ and Ie) in\Or,;c filtering "ilh application of 11~nninl! wintl<;M'_
". , .. .. , ".
" , . • • " I ,. I ,.
" •• ..
,. -10' R~,ul' trom ",,'cl><d (,iocrrd r",,~< ",,,fib In) 11","1, (Tn'" mJl<!>cd fi,,,,.d. "tin foC, "'''0''''
"1'1'1,<'<1, ""'¥< p",~ I ..
.. • • • • , ,. , . ..
1<, ~<'tli' I".." 1m'"",. fi ll<",d. ,,"" ,,,' ""><I,,, .. "I"id) R.,"II f",m in,',,,,, fill<r<d. r,><rt. r:rn,,< I'",fil" dow ' ppl,ro . ~< prn~l<,
Figure 6.9: [kamformcd ima~~ in lh~ ,'a"" of m~l~heo.l fil!~rong 3nd invc~ filt~rin>!_ "jlh Ill' apenun: ..... eighting •
• ,
to; Hcamfo,m<tl ''''>g< Ib, Fon-bc.un j,no;«
Fi~"rc 6.10: Bc;,mll'rm,·,j "',ag'" "hen HH,"'m~ "r,,'c1l1r~ l\<" ,g/l1 illg ;, "ppiicd l<llhe Hanning-windo\lcd. inl'er.;..: fi ltered Sil!J13 1.
70
6,2 Mullipll' Targl'ls OCfcl'tiun
In Ih;~ ~;mulal ion. ~;.~ lnr~~1.1 Me plac"d ,n 1""11 01 11w 1"Ii<i!r. "nio \ar};cI I .,'" llIfJll"1 ~
~pao:ed 15 ~m a",~~ limn ~I,"h Ollie •. Inh'ri~ I,il, ... rng. "lih ~bnn;njl .. ""l<.r",;) applied
10 en..h oflht.> 8 ran8~ I ..... ~fil~. (~, Ih,· ..... ~,.<' H re.:eiv;'\g ,·I,·m.:nlSI. ~"". Ha,m;nl; ap.:11.un
'H:ighring i.1 u"'-'\! In Ii:>.:us Ihe ha"-b~,,JL'<III',",'''''' I1lic",rI 'igna"- Fil;l/f~ 6_11 mv") Ih~ cnm~io;on ""I"....., I~ ft'Iu:,llo.:a l"~,, ",fll"' ! "'~'·I>. "lid Ih~ rL'CU\'-.J rail-beam im~c
ot Ihe pm.;<"MN f~'Iu lt. r h~ ..... ,"11 trom II .... lun.I ..... It! llturile I:i\ ,., ~ d""e ~ppru\imaIi(ln
10 Ihe Io.:alion of lhe tal'K~l$ I hL' ~nglilar r,",,,I\,I,,'11 "Mil he i,npn""'\! h} i""n~a>;n); lh~
length ofl~ IITra~ "hi. h ...-qui,..,. inl,,-.Ju • .:illg .... 1<1'1'''''1111 dcmml' if lh~ allgu la' Hmhi~\I·
,I;I!-'; Igr.mns Inl>t. ... ) nn: ''''I In I)<' 111.,,;:1<·,1
" . " i . ,
•
'--- -_ . ~ou.,"~E_"''' • , ..... " 1., .. ,
• -" .'
" .. ,. . .... '".
001/
OIl<
"" -I· ill"'!\." 6.11: ("l11l'anng lhe procC'lSr.-d .-.::_uh " nh II .... '" .,,,;.>1\ "I Itr~ lurg"! ' I"" .(0,'<1 Inr!I~Il}
"
C hapter 7
Results
In thiS ~h"PICT. !he perforrnan~c ",f the L' WB >~ SI~1l1 h~r,J"~re i~ ~,,,,,,,,,,,,,l ." ... 1 \ '3,,,,,,,
lnrlt~l deteCTion !.Ccnarios ar~ inl'esl i~~le d,
• :'101111 ,1>, o,er time
In 1 ~ IMgtt de\l'\:ltVn s«IIOO. the !lIlli ll} 0 1 Ihc U ~ B nIt1ar for dc-te("ung 1at'){C1 ~ ... uh dil
Icret1II)~ of mlllc'Ial and for 'MO" inll cICl>C'·h~ ~itionro uIJgc1s i~ nam",cd. later,
;'>I~,inl is pl'ffocmQj usinll t 'QU, clcmmt UYVB rt'c"'\t'r 3rT3y T¥bl., 7, I »how. , ..... I ... ·
lIel (')objects In" are II~ In Ik (\penmen",
7. 1 l lWB :11l 1 (> lIn ~s
T"o I}'pe~ Qhnlo:1'll'l!l. BK I,IstJ in Ihis lhrsis T ..... fir!.ll) pc {·f antenna i\ thor h.'\Hie an
ll'11na H[lllll." 7 I ,00", the" '\\0 bo""ioc: ,,"lcnn~~ lhal .. ere 1101111 h} an unde"gr:Wl11I.le
thesis IolUiknl in 1004. n..:"" il" Ic:lIl~~ are .1e.~iK"eJ ti'I opcr.ue iloety,'een 1 ~nd 2 Cil I7
(\8. q]
In,~ In eXAm;" .. the IInlrnn~'s fr~uenc} NSpo.lI1SC. SII and 521 measull'ment.. usintl
net" • ..-i; M:lIYUI. "CK perf{)nned Iln the 'ell" -lie anienn:l. which art' ~h..,wn in Fii/.ur<: 7.~ _
the tWO bow,ue lIIl!~M~:Lr~ h~ IJ 2 m :;apan, I igu!T 7.2 ~huwj that in !h~ ul'\',-"lin" rrr
"""no:} mng~ Qr I 10 2 Gllz. the r~um los~ of lho: bo"'·li~ "nlenna i~ brl\'~m -S dB
and ·20 dU. lh~ Inll1$mi~silJll ~ain il "ppm~lnlllld y -22,5 dlJ Huwe''''". Ihe g~ i" 'S 1101
r .... SlIllH bel'H"n I ~l1d 2 GilL "'h~r~ Ih,' I!it(n ,larll 1" \k~n:;,..., 1I II> (,II,. r rx. 1 dB
" "
, M..-wl Grid X ;11, "')11
500 p.:r side
Tabk 7. 1: M"tal objC"l:I5 usc<.l in the e~p ... rimcnts.
,., flore .n iJe ,m . lI<r than ~o dc~",<
I h~ S<.~ond 1)0 pc of anlenna ,s lile Vi, aid, antenna. II is a .;;P"'=,31 case of J lapered slot an
tenna "ito an c\ponentialwpcr proftl~ 1441. Thc Vi'ald; al1lCnna~ ha't large band" idill .
I" .. <.Idili"" . • h~ Vi~~ldi U"' ... ",, .. ,:or<: li!!I" well!hted :",0.1 ~~fl he ~",il) r"h,i':""d ",;Ill!
I'rinleJ circ ui l bo,)ard t<"<:hnok,&-,. fl,c~ ~ey fa(.·\"", malo. ... Vi"oldi "nlcn,,~ u dc,ir:lhl~ J".
I~nna 10 usc in this Ihesis. Se'eral Vi\1l1dl antennas "e", a~qul red from a prc;-iolls pmj,-';l
,,,";cd OUI "ilhin our <.Ict"lMmcnt. n.c,c could be u~ 10 fOllTl 8n am}
••
--, -_ ...... 'OJ SII
• .. ,
. 'I ..
!, , ,
• i~U(~ 7.1. lUI ~II !II1J (I» "~I rncas urcmcilu of m " tx",,·, i(',1Illenn;os );lC lng eJ.h Nh~r ~ I ~ m nran, The 1"'0 mar~crs in lb) .. ..... h.ocal ~1l kit 1 Gli/ and 2 Gil, Frcql'c".y nl1\~c (,.,,,,, /. ll ~l ~ 11 / 1o' ~ ~ GI'l, Venk~1 u.\i s la): .. ~ I' In sn dB ( 1IJ dR,d;,) Venl eR1 a~i s (h): ·70 111.10 dfl (1 0 dB di~ J
ri~ure 7.3 ,ho"'~ lh~ Vi. ,.kll alllt"'~' 11 .... ·,1 '" .t>" I h.;s l~ and ~Ig""" 7 . ~ ~h<l" ~ Ih~ S II MId
..,21 mea~uremenl pcrforrn,1() h~ U>Hijll "'1 Vi. ,, 1,1. anlc"",1 "'It>"lg ~I ,,;och ,,,ho,:f ..... h ... h ;~
placed ,II ~ m Ipan. risun' 7 ~ ~ko"" .hl I Ill: H MI1~uli"i(l" 10""1 '~"I"I'tO \'''I.lI .. l~ • ,'U IlH.
in t~ r~'1llC'nq barld of SOO ~ !l llio 1600 MilL anJ appr..-"i",.lcI~ -10 tl A lran,m"," '"
gain in 1ilc f""luclle., band of ~ Gilt 10 7 Gf IJ: 1'he Vh lid; antenna ""~ ~ ",h.m k'!>l> of
""ncr Ih~n 10 dB fill' aJi rrNucn, ~ aNr.c I Gilt ~hc"' ; n~ thai ;1 i~ "ell rn..IC ..... <.I III SO 0
(l' er us " <.'1\.. '" ); r~n):e
I .~ure 7,.1: A ViulJi anICflll.'.
': I
::} 1 - 1" .~
,. , ,.
(0) S II
ri~u .... 1.4: (31 S I I and (b) S21 mea~,,",menI S (If 1'"'0 Vi~ald; ameMa~ fa~t!lg (,;I.,. tH\Ih.!r J! ~ m ~rart Th" ("Q 1]1:Ifi..rrs in (b! arc k",:aleU i>l I Gllr. ~r>tI1 GI [;. I requ"tlC) rang .. (~_a_,;,): 3(111 ~ II; In H_ ~ ( ,II,
Vertical a~is (al: -60 10 40 dO (10 dO,d" I V~1't,~,, 1 a\., V'I: ,,(.0 ti> 40 dB ( I f) ,tR:Ji., i
1.2 S)'Slem rcrforll1:lllcc Melisurelllcnts
7.2 .1 Noise Meltsllrt'menl ur Ihl- lJWIJ Rtcei l'U
I n lite I lWEi mdar 0) 11<"1". lh,-...:Ix> tn'lll1 a lar~CI " .,n~" !>I,ried "!I,d" Ih(' Ihcrnut!) roJi·
" led "oi .... In)", It..: ."':"rlC 11.:".:.;:.;,,, , "ll'·"n~"1 )" "" I1Ullll~ I h~ nub.: " nlt in Ihc rc .. "" c.
~i«:uil aI I ...... , . 10 a I~el ~I"" lite It"'flnn ll~' md"ucd "" 1'<: 1n.'"1 Ih~ .... ~II(', f ...... " l<\~l
Indoor- Ima~",s art>li' alion.,. 11", r«.". 'PIg a"ICII"~' "h",,, C l)/'J"h Rl !\>(>!1l I('mlll=ffliurc.
around 300 hI. lB.
' ':>;Sf" ~ur.:mCf11 S are ~rfOllTlN alOoI /!. Ih~ ,ari"II' poi"" in Ihl' lJ W Ii I'e.:ei,~, ;; ire"i,
r he IC'SI poims are ilhml Jle In f '8u~ 1.5, fh" e:.perime", ;, uil1leJ 1,1 id~,"if~ thl:" (~)mi.
nam ""i'OC' flloCtOI within thc Ittci'·cr. " h,ch '~tI..elul f", fUlIJre dc, el.-.pn~ nl
.\, each ~agc of tl>e npcrimCflI. a d iffn-enl co ndition IS pl3{cd rm the tC'St ro ln lS ~M" 11
in f i~urc 7.5 111<: n:1>II 1t from each st3~e is obtaillC'd b, me:!St!I'lIl!: Ihe OUtput III Ihe ADC
mcod"k The ""Ipul of thee ,\IX is n-<:orued in a rrome·S!> Ie. "h~ each rrame consists
"f ~-lO '>IOl11plc ",,,nb a"d (".och SIImr k !'O'nt rorrt"~'fld~ 10 a 0.15 ns lime Slep. I h.s i~
'-"'llti,a'e'" 1<' a I'.n~c r ...... lik .. r ' • :~,. ft/' . 1(1 , "" 5 -l m The: otllpt.a of ,\ DC is recordN
:II a nne "fl":1 rram .... f'<"I" ~.,,,d. a,,j a 1"",1 ,,/ ~ Irnnl(>, an: nxonJed per ('och 'IHg~
of e.\p.:nmcnl rr>r C'llrn Ie,.. POlnl,
III 111 ~ fiN sla!>c " rlhe C'pet"im~nL l(~l poinl Ilinpul Of lhl' AD( modulel i~ cnrme.: leci
,,, ~ 1.1 V 1)(" wl'lll~ Th~' IX: '>lI N lt) , ~d~'lIploo with ISO nr 1111:1 J5 nr cap3{il{ID H>
rcmo'c ~n.' f'>"."hlc .)!;cdlat;"H' at", ""i", ill !l1I.. 1>t!pp1~' rigu .... 7 6 . .JJo><~ thee lTt ... n 3,>d
"
!Programmable Delay Module
1 Trigger Generator
'" V 1 i
Front-End Amplifier + Integrating Sampler ~ Post-Amp.lifler -r ADC Gain =40dB \ Voltage gain = 1
1
I , ,
Point 1 ,
'. Point 2
Poinl4
Figure 7.5: The test points in the UWB receiver circuit, which are used for the noise measurements.
the standard deviation of the ADe output voltage, calculated using 500 frames.
l.30
2.25
2.15
2.10o!----;;;:50--~100;;----;:150:;;----;200;;;.----' Delay Step Unit
(a)
0.0024
0.0022
0.0020.
o.OOle)
O'-·O!----50;--~~;;---.. ~:;;----;200=-~ l:>ltay StllPUni(
(b)
Figure 7.6: The (a) mean and (b) standard deviation of the ADe output voltage, where the input of the ADe module (test point 1) is connected to a 2.2 V De supply.
In the second stage of the experiment, the post-amplifier module is connected in front of
the ADe, with an offset of2.5 V added to the ADe. The inputs of the amplifier (test point
2) are connected to the ground. The effective gain of the post-amplifier module is set to
one. Figure 7.7 shows the averaged and standard deviation result.
In the third stage of the experiment, the sampler module is connected in front of the post
amplifier module. While the input of the reference sampler is connected to the ground via
a 50 !l resistor, the input of the integrating sampler (test point 3) is connected to (1) the
ground via a 50 !l resistor, or (2) a bow-tie antenna, which operates between 1-2 GHz.
The antenna is aimed at a brick wall indoors. The waveform recorded at the output of
the ADe module represents the response of the input device connected to the integrating
sampler. The mean and standard deviation of the recorded waveform are shown in Fig-
76
BO
~----------------~ 2.25
2.20
2.100:-----;,-----;I00I:;;---.lS"'O-------;;;::-----.: OoIoy_Unlt
(a)
0.0024
0.0022
0.0020
0.0012
0.0010
~-~:---~~~-.. IO~O-~lS~O-------;=-~ Ooloy S..., Un"
(b)
Figure 7.7: The (a) mean and (b) standard deviation of the ADC output voltage, where the post-amplifier module is attached in front of the ADC, with a 2.5 V offset added to the ADC. The inputs of the post detection amplifier (test point 2) are connected to ground.
ure 7.8 (for the son resistor) and Figure 7.9 (for the bow-tie antenna) respectively.
2.30 0.002.
0.0022
2.25 0.0020
'> ;; 0.0018
J 2.20 ~
'
0
.
001
•
2.15 0.0012
0.0010
2.2°0 ~ 100 150 0.0008
0 100 ISO ;lOa l)IMay Step Unit o.leySt4lpUnil:
(a) (b)
Figure 7.8: The (a) mean and (b) standard deviation of the waveform recorded at the output of ADC. The sampler module is connected to the post-amplifier, where the input of the sampler module (test point 3) is connected to a 50 n resistor.
The noise standard deviations shown in Figure 7.8 and Figure 7.9 have similar value, in
dicating that the antenna's received noise is similar to that from the 50 n resistor.
In the final stage of this experiment, the front-end amplifier module is attached to the
sampler module. The input of the front-end amplifier (test point 4) is connected to the
bow-tie antenna that is used at the previous stage of the experiment. A total of 40 dB
gain is provided by the front-end amplifiers. Hence, the recorded waveform contains the
amplified response of the scene (received by the bow-tie antenna) and the noise generated
from all the module in the receiver circuit. Figure 7.10 shows averaged and standard de
viation of the output waveform. Note that in all these experiments, the transmitter was off.
Table 7.2 summarizes the results obtained at each stage of the experiment (at each of the
77
2.30
2,25
2,10o:-----,';50:-----:100':::;:----:-;,15o,,-----=200:::--------' DGIIIy StItp Unit
(a)
0,0014
0,0022
0.0020
;;; 0.0018
i i 0.0011
0.0010 '
.,0008.:------.::--""'1000;;----150::-:::-----::",------' DoloySbopUnR
(b)
Figure 7.9: The (a) mean and (b) standard deviation of the wavefonn recorded at the output of ADC. The sampler module is connected to the post-amplifier, where the input of the sampler module (test point 3) is connected to a bow-tie antenna, which operates between 1-2 GHz.
no
s; "& i 220
2,15
uoOb---=--.. l00;;;----,;;:;S.~--=----' Debty stop Unit
(a)
0.0022
0.0020
s; 0,0018
1 Il 0,0016 J
0.0014
0.0012
0'000GOb--~50:----"10~0--rr.150---'20~O-~ Dlilay Satp Unit
(b)
Figure 7.10: The (a) mean and (b) standard deviation of the wavefonn recorded at the output of ADC. The front-end amplifiers are connect to the sampler module, where the input of the front-end amplifier (test point 4) is connected to a bow-tie antenna, which operates between 1-2 GHz.
(
78
4 points shown in Figure 7.5). CTaverage is the averaged standard deviation measured at
each of the 4 points. These results have shown that the front-end amplifier module is
the dominant noise factor in the receiver. Furthermore, the front-end amplifier increases
the amplitude of the received signal, which makes the distortion caused by the noise in
the receiver circuit, less significant. The second dominant noise factor in the receiver is
the post-amplifier. However, by adding the sampler module, the noise is significantly re
duced. This shows that the sampler can effectively remove the thermally radiated noise
presented to the receiver, which otherwise could be amplified by the post-amplifier.
Stage Stage description CTaverage
First Stage ADConly 1.38 mV Second Stage ADC + post-amplifier 1.64mV
Third Stage (1) ADC + post amplifier + sampler (connected to son resistor) 1.40mV Third Stage (2) ADC + post amplifier + sampler (connected to bow-tie antenna) 1.38mV
Fourth Stage ADC + post amplifier + sampler + front-end amplifier 2.16mV
Table 7.2: Summary of the noise performance at various points in the receiver circuit.
7.2.2 Stability vs Time
This experiment was conducted to examine the drift in the UWB radar system over time.
Knowledge about the stability of the system is important, as during the radar operation,
a snapshot is taken prior to estimating the background clutter in a testing environment.
This background profile is used later to remove the background clutter from the raw tar
get response. If the system drifts significantly over time, the subtraction of background
profile taken before the experiment would be unable to remove the background clutter
from the raw target response effectively. Details about this operation will be discussed in
Section 7.3.
In this experiment, two bow-tie antennas were placed at 30 cm apart, and were attached
to the UWB transmitter and the receiver circuit board respectively. The response of the
scene was recorded at the rate of one frame (Le. one range profile) per second. Figure 7.11
shows the system setup for this experiment.
In the first stage of this experiment, the measurement of the scene profile started immedi
ately after the circuits were switched-on, i.e a cold start. Two pre-amplifiers were used,
in cascade, in front of the sampler module to provide a total of 40 dB gain. The post
amplifier voltage gain is set to 16. A total of900 frames are recorded, which corresponds
to a measuring period of 15 minutes. Figure 7.12 shows the voltage recorded at the 50th
sample point in the scene profile, over a 15 minutes period. From the result shown in
Figure 7.12, a temperature related drift is evident over the first 5 minuted period. Hence,
79
1 igll~ 7.12: Tht: meB~urcJ mhage III lhe ~r'~ .. ample 1""'" in I~ 'CC'r~ p,unk .,'·C'r a fIC,,,-.I "lIS n,inu'e-;. n", ""'~$,.-.,m"'" <l3n~1 Im"",dj,.",I} ~fl:~, IIw/ eireul •• at<! ~"i."'",J_
"". r n (1M: >1,,,,,,,,1 ~11tHe "r (hl~ e~r«''1l('tu. 'itlll fram"" of the ~e p'nfiie "~I~ ~':onkd ~f·
ler. " ..... '1-"1' pcrroJ, for I"" e.....,.rOnlc ~;,,: .. !I, nf)(I mlln.!~, The , '3n31;on or Ihe sc:c"t
proill.: "'e""" [l<'1ioJ "f 15 minult's i~ dlSpl3) cd in I igun: 7, 1 J H¥Ut.: 7 13 )h",,~ 001)
>~'en oft~ ,«,.,ded profiles su~rimpusw. m:Ulded 8' 3 m;nU(" illl\'I\.I" 1M ,'"Ii un thi. scale ,5 b3rel, ,'isible, .".. s.anJard Uo.', 1111;,,,, uf tI", >"tn" prvlrle "a~ ,.I~uI3Ie.J
USIng ~II 900 prufilo ""d Iht ~ull ;,. >h,,"'1 in F,!!ure 7, t4 n.., .I ... ;all"n In I"" ~;gnal
o~I\ed ,n 1 iJ;uf\: 7 14 i, Ih~ Imnnall) r.,,'i~lcd ",-,i", rccei,ed h) the ,«d"c., as "en as
til<' n,,~ " I (he ...... c;'n ci'\:U;t
110c le,ull ... nl""incJ f'nm b",h figures, six,,,, Lha( tht rc.:LJrdcd pwflles remained r.:1~
",'cl~ MDIII .. aner It!..: clccmmlc CLI'I.'uils have been wanncd.up. n.., c!lkululCJ HanJ;" ..
dcl' IBIl"n 31 tile OUl pUI of ="',' .. r IS 3'uunJ 5 mV ..... hith is occq>l~ hk. CI.)I'~Jlk,;ng IIr~1
&0
" ... ~ .. l !.«""" ! .. ~ .. lOu """on,,, 1 Nt .. l5C ~"""I • I ..,... '"" ""''''' ... ., - Aft" ':: s..", • ..., I .. ~ .. --"" ... I
j'l- - ~.- > 1
' .. "~. 1 , .. , .. I '1 I • 'W \" ,..., .... ' ....
Figure 7. 1.1 . I hi , graph .d,,-.... ~ ~~" en pmfile.~ ~"Jl"ril1lpo:;ed. The pr_ )files "ere recordM at e' cry J minules. 1 he responses were rccrorJed after the eiectn:.ni. circuits ~ad wlInneo.!-up "'1' l() mllHltc<
,~: '. Figu re 7.1~ : The sundar.! dC';"';,l l1 of t"" S~~nc pr"fil ~ me, 900 fmnk'.'. "hich i~ CJ[>lUred ,,( "n~ rr3m~ per ,,"'()flJ The seem: pwli Ie, "'" "-,,.,-[kJ Hn~r I ... · ckeITon,,' circuits h.)," 1><.",,, "anTI.up 1<-.r lO mim.LIC~
the test target gave peak-to-peak responses of around 1000 mY, as will be shown in the
following sections.
7.2.3 Signal-to-Noise Ratio Measurement
The aim of this experiment is to determine the SNR of the UWB system for typical short
range detection applications, before and after signal processing is performed. The SNR
can be calculate with
SNR (Vrx(pk))
2
( O'noise)2
where V rx(pk) is the peak voltage of the received signal from a target, and O'noise is the
standard deviation of the noise.
In this experiment, two bow-tie antennas were used as the transmitting and receiving an
tennas (Figure 7.11). At first, a background snapshot of the test scene was recorded. The
experiment took place inside a laboratory, where the length of the laboratory is approx
imately 6 m. Office tables and chairs were situated inside the laboratory in rows. This
background profile contains the echoes from the stationary objects, i.e. furniture in the
room, as well as random noise. 500 frames of background profile were recorded and av
eraged. Thereafter, a comer reflector (see Table 7.1) is placed 1.6 m away from the radar,
and 500 frames of raw target response are recorded at the rate of 2 frames per second.
Figure 7.15 shows the mean and standard deviation of the raw target response and the
background profile that was recorded at the start of the experiment.
From Figure 7.15 it shows that the standard deviation peaks at the distance where the
comer reflector is situated. Although the comer reflector was placed on a flat stable sur
face to minimize movement during the experiment, however, the wind blowing into the
laboratory and other vibration probably caused it to change its position, hence explaining
the peak.
When the background profile is subtracted from the raw target response, the true echo of
the target is revealed. This is stored as the reference signal, which will be used in the
signal processing in the later stages, as explained in Section 3.4.2. Figure 7.16 shows the
reference signal, in time and frequency domain, that will be used in this section. This is
the echo of the comer reflector that is placed 1.6 m away from the radar. The spectrum
of the reference signal is band-limited by the bow-tie antenna used in the experiment.
Hence, the spectral components between 1 GHz and 2 GHz are stronger than the rest of
the spectral components.
The peak voltage of the received signal, Vrx(pk), measured from Figure 7.l6(a), is ap
proximately 0.4 V. The standard deviation of the noise, O'noise, which is measured from
82
2·
-1
-2
(a) Averaged background profile
-1
(c) Average waveform of raw target response
~ow,---------__ --______________ ,
0.008 '
M02
n-o~---7----~----3~---7----~ _m)
(b) Standard deviation of background profiles
0.020,---------__ ----____________ .,
0.015
0.010
0.00°0):-----7-----,-----3:-----7----.....-----' AoI19OlO11)
(d) Standard deviation of raw target response
Figure 7.15: The (a) (b) background profile, and (c) (d) the raw target response ofa corner reflector that is placed 1.6 m away from the radar.
Reference ~gnalln time domain
2.5
2.0
1.5
1.0 -1
0.5
-2
(a) Time domain
-3
Reference signal In frequency domain
o Frvquency(Hz]
(b) Frequency domain
3 xle9
Figure 7.16: The reference signal, which is a target response of a comer reflector (see Table 7.1) that is placed at 1.6 m away from the radar.
83
Figure 7.15(d), is approximately 0.005 V. Hence the peak: SNR of the target response in
Figure 7.16(a) is
SNR ~ (~)2 ~ (80)2 = 6400 0.005
Signal processing is performed in the following steps:
I. Subtracting the background profile recorded at the start of the experiment, from the
raw target response.
2. The spectrum is converted to an 'analytic' form zeroing out the negative part of the
spectrum.
3. The background-removed target response is them processed using an linear filter
constructed from the reference signal (shown in Figure 7.16(a».
Two types of linear filters were investigated: a matched filter (equivalent to correlation in
the time domain), and an inverse filter. These were described in Section 3.4. Furthermore,
a reef window is used to band-limit the filtered signal to a 1 GHz bandwidth, centred on
1.5 GHz, for both matched filtering and inverse filtering. Figure 7.17 and Figure 7.18
show the results from matched filtering and inverse filtering respectively. Since the signal
is in analytic form, the time domain is a complex signal. Figure 7.17 and Figure 7.18
shows the magnitude of the waveform in (a), the positive frequency spectrum in (b), and
standard deviation of the magnitude in (c).
It was noted that in Figure 7.17( c), the standard deviation has smaller peak: than in Fig
ure 7.15. It is suspected that the frequency component of the peak: noise in Figure 7.15
is higher than 2 GHz. Hence, in the case of Figure 7.17( c), the high frequency noise is
suppressed by the filtering.
Table 7.3 was constructed to compare the SNR performance before and after the signal
processing was carried out. The results shown in Table 7.3, were extracted from Fig
ure 7.16(a), 7.15(d), 7.17(a) and Figure 7.18(a). The table shows that with the usage of
signal processing with a filtering technique, the peak SNR is improved from the unfil
tered result. Of the three cases, the matched filtering give the best SNR performance (an
improvement of 4.8 dB (lOlogl~~». However, the matched filtered output signal has a
wider pulse width and irregular shape compared to the inverse filtered signal, which is a
Si~X) function. This is due to the fact that the frequency spectrum of the inverse filtered
signal (Figure 7.18(b» is a reef function. When transformed into time domain, the inverse
filtered signal has a Si~X) shape, which has narrow mainlobe. The improvement in SNR
for the inverse filter over unfiltered was only 1.5 dB (lOlog~). Based on the above
mentioned observation, inverse filtering was chosen as the signal processing tool for the
later experiment, as it provides a better peak: SNR than the unfiltered method, and has nar
rower main-lobe than matched filtering, which is importance when ones tries to resolve
84
0,35
0.30
0,15
;: 0.20
J O,IS
G.l0
5
I· s'
) x109
(a) Magnitude of the averaged wavefonn in time do-(b) Magnitude of the averaged wavefonn in £re-main quency domain
0,001
0.001
o,oooo!;----;----;-----,);------:---~
_ml
(c) Standard deviation
Figure 7.17: The results from matched filtering the background-removed target response.
85
0.20 1.2
1.0 0.15
0.8
0.10 i Q. 0.6
i 0.4
0.05
'ArJi ~f\fI" 0.2
0.000 3
0.0 ·3 ·2 ·1 0 3
Rangelrn] ~u.ncyfHz] Xle9
(a) Magnitude of the averaged waveform in time do-(b) Magnitude of the averaged waveform in fre-main quency domain
0.005,---_--------_--_---,
0.004
..... 0.003
i j 0.002
0.001
0.ooooL--_--_--_3-----.,--_--.J Ranlll".tm]
(c) Standard deviation
Figure 7.18: The results from inverse filtering the background-removed target response.
86
targets that are placed closely. The sidelobes shown in Figure 7.18(a) can be reduced by
applying appropriate window function, such as Hanning window.
TI' O"noise
v n:(pk) PeakSNR 0'",,;.,
Unfiltered 0.4 V 0.005 V 80 6400 Matched filtering 0.3075 V 0.0022 V 140 19600 Inverse filtering 0.1529 V 0.0016 V 95 9132
Table 7.3: The SNR of the received signal when signal processing is used for the case of the comer reflector positioned at a range of 1.6 m.
7.3 Target Detection
The UWB radar is operated with the following steps during target detection:
1. System setup:
The user must input the parameters of the radar system that are used in the ex
periment. The parameters include the number of receivers used in the experiment,
spacing between the transducer and the data acquisition interval, i.e. the time be
tween each caption.
2. Background clutter acquisition:
The noise and the information about the stationary objects in the scene is captured
at the start of the every experiment. 30 range profiles are recorded and averaged.
The background profile is then stored and can be used to remove the background
clutter from the raw target response.
3. Reference signal acquisition:
The echo (signature) of the target is required for the signal filtering process. Since
the echoes from different targets possess different shapes, therefore. range profiles
are recorded for all obj ects shown in Table 7.1. 30 raw target response are recorded
and averaged for each target. The averaged raw target response is then processed
by subtracting the background clutter from the profile. The background-removed
target response for each target is then stored.
4. Setup the frequency band of interest:
The inverse filtering method is used by the om to process target responses. Since
the inverse filter is only defined over a bandwidth, hence, the user is required to
specify a frequency band for signal processing. The default value for the frequency
band is set to between 1000 MHz and 2000 MHz.
This section is divided into two sub-sections. In the first sub-section, experiments are con
ducted for detecting objects using a single transmitter and a single receiver system. The
87
mUcnna.' u.<;Cd in this ~ub·s.,('1i"n an.- tile t\\'(' bo.)\\ ·tie anten,,~ sho .... n In riguI"C 7.1 I. In the
.....:ond suh-!;c~ti('n. Ihe C\pcrim"nIS c<'nJuctro In:: aim<:(l at " bl3lning bc.mfl)rmtd im·
age' and dC I.'Clin¥objellS thmulth a brick "aiL The rad~T ~}sl ... m u~d in t/l 1.< )ub-~.iull
,,,m.<i~l~ 01 tnur \'i,-aldl PCB arneJ\l\J..\. '" h"h " ctc used ;IS tm- ,.cn'II' inll- anl~nn;as. :II'Id ~
bo ...... _I, .. anl"l1I\lI. "Il"h 1"""' us....J lL< tM Irnr\.-.n illlrlll- Il/l.,·nn~.
I).., Vi,-ald, PCH ,nlcMa.< are Ileld in place b} ~ "ood..'11 base. "hich h;lSSlol~ cut·m Iu
til Ilk- "'lIcnl18~_ F....:h ,Ioe i~ 5 em apan nc t • ..:e;'~t 'ircuit board ;s~" n """cled dil\.-.:tl~
I" Ill" ~mcnll~ ,ia a 5<J n :'.MA CNln.."-:IM. f I~ure 7.1'1 51l"",! IIIe UWB ~rrn} mllar !ol1 Up.
1h<',h>lHOC~ h.1 ...... cn It..: oojoccml'l II "nlcnnas i ~ ~ppm~;muld)' 15 'rII, "h;eh is lim,
Ilc<l b) lh" sp....,in~ "''1uin.-J I~-.r lho: tee"" cr l"xu.J "hen Nnr><."-: I~d 10 ttll" nnl"nna,
F,¥un: 7, 19: lI WH dlTll~ ')"CIrI u~;ng hlurVi,'a ld ll'll:l WlII.'Ilrul>nnd a bo\I·ue Wllenna , I II" l .... nMnlllcr Pt I:l is ,' i~lbk on the kft side and Ihnl...-:e;, er PCIf ~ hl\C ,;"ble, 1I1I1'('h .... J I,' the fl.'In \r,Hld i ~nl~nna~ n,,· AlX "ncn. .... "lllrolkr ~IId del") Imc P( Hare 001' ,'ihk
'" Ih" Ph, lun:
7 •. l , I i\hn il1l lllll 1{:III l!l' I)dl'l" iun For A ~m;lll (550xJ91)mm ) 1\lda l
(;" iLl
n", nJ'<-' """,nl i. a"n~ al d.)Iemllning Ih~ maximum 1'3Il~'I: for oktee. ing 3 $fllaU mrul
~riJ I ~~'I(.i90mm. ;hov. n III fable 7_ 1 J. " ,.holll the n ..... -.I to ;n • ..,,,,,,, Ihc l'I"'I-81l . rl ,I ... ·t
!>11m ~tM \ 0 11311-(" gain o f Ihc II'-'>-I .... mpli!icT is "'" t., ~>n.:J ..... N<.kt;I''lJ11J pmh!.- ".1'
~ apiun-J ~I Ihe ~I art ,·r Ihe ,'~po.·r;mcm Th~ .. _ M ""'Mil mct~1 grid I' "-< ph,,, ... 1 ,,' I"",t •• 1 the
rJd~r l'igun' 7. ~O ,"'"" th~ ba.. ~gn'IL"'d l>ffiIlk ""0 Ih" 111\0, Llfy l ......... ponsc nf Ihe $m31l
m.'tallln<l ~I 2 m a"~' r",,,, tll" .... b .
11 .. , ' lII~tlIIIClnl ir;,1 "," IMn l:lO\cd lunhc r a,\U~ fror.l Ihe r3J:u In difti:n:m po.~itil'n~
11K' tmc~ gfllun,1 Ilfonlc "&< th'~1 used I" ~ubtroci the ~3d;groun<l duner from the 13"
~' 'tCl te~polI~. ~ ;!lure L! I sh(',,~ the ha.:kgrowld·rcmvved t~"'t ITspon5C of the Imlul
gn.J, "h I~h "iI.~ pla.-:1:d al the distance of:2 m. J In. -I m anJ S m ""11) from Ih..' IlId~r
, ,
I : c'tr","Nij\\,~
I • -- "-'"
Figure 7.~(j: Profile shows Inc (a) tm.;:kground anJ th<; (bioII'. tal"f."( "'~I"'r"~ or Ill<: "mall mcul:.;:,id . "hid, j, p'JSilionnl at: rn a,,") 1'",,,, In., ,.da'.
, ,
.~
, f----~ I
--Fi llur~ 7.2 1: Tlir!.:cl re~[l(.l"»; ~'f" ~ma ll n.,:(al ),,'rid. whi~h is platd 81 ,-ar,,'''' d i'lance a"a~ from m" largo:L
Figure 7.21 shows that the target response of a small metal grid is clearly visible at 5 m,
without the need of signal processing or increase the gain of the post-amplifier.
7.3.2 Target response of various objects
In this experiment, the target responses of all the objects shown in Table 7.1 were acquired
and investigated. Although target classification is not addressed in this thesis, these target
responses, which contain the signatures of the targets, can be used for future research.
Figure 7.22 shows the background-removed target responses of these objects, which were
positioned at 2.2 m. The standard deviation of the noise, which was recorded in the pre
vious experiment, is approximately 5 m V on the raw signal.
-1
(a) Large metal grid
, ~e"'J
( c) Corner reflector
(b) Small metal grid
i f·r-----~~---------
(d) Human
Figure 7 .22: The target response of different targets. The target is located 2.2 metres away from the radar.
Figure 7.22 shows that the target response from the metal grids have similar shape. Fur
thermore, the target response of a human is more elongated. Table 7.4 shows the peak am
plitude of the target responses. Assuming the peak voltage decays proportional to Jb, then
Vpk(R) Vpk(2.2m) x bfr. The rangeRmax at which the SNR=I, i.e. Vpk(R) = an = 5mV,
90
is
Rmax(SNR=l) 2.2
- y'Vpk(2.2 m) x va;,
- J(Vpk(2.2 m) x 31.1 m
The range Rmax at which the SNR=IO is
Rmax(SNR=lO) = . IV, 2.2 V pk(2.2 m) X . I ITi'\
V V lOan
VVpk(2.2 m) x 17.5m
Table 7.4 shows the calculated maximum range of detection for various objects, in the
case ofSNR=1 and SNR=IO.
Target Vpk of the llIrget response (positioned at 2.2 m) Maximum R (SNR=I) Maximum R (SNR=10)
Large metal grid 1.62 V 39.6m 22.3m
Small metal grid 1.12 V n.9m 185m
Comer reflector 0.21 V 14.3m 8.0m
Human 0.21 V 14.3m 8.0m
Table 7.4: Amplitude of the target response of different target and calculated range for V(R) = an (SNR=I) and V(R) = JIOan (SNR=IO).
7.3.3 Range Resolution Test
The range resolution experiment is conducted to verify the range resolution of the system
when a I GHz bandwidth pulse is processed, occupying the spectrum range from I GHz
to 2 GHz. Two targets, a small metal grid and a large metal grid, are located in the scene.
The two targets are placed IS cm apart, with the small metal grid closer to the radar. Fig
ure 7.23 shows the background-removed target response of the two targets.
It is difficult to distinguish the two targets from the range profile shown in Figure 7.23.
Hence, the target response is processed, using the inverse filtering method, with a pre
recorded reference signal used to fonn the inverse filter. The reference signal used in
this experiment is the target response of the small metal grid. Figure 7.24 shows the in
verse filtered target response. Two windowing functions, reel and the Hanning window,
are used to band-limit the signal, which is required for the inverse filtering and shape
the spectrum. Both windows are centred on 1.5 GHz and the bandwidth of the window
is I GHz. The results shown in Figure 7.24 confinn that a radar system using a I GHz
bandwidth band, has a range resolution of about IS cm. One is able to visually resolve the
two targets in Figure 7.24(a) but with undesirable sidelobes. The Hanning window sup
presses the sidelobes, but broaden the mainlobe by 50%, causing the mainlobes to overlap.
91
~ f o~ ______ ~~~I1II1~~~~~~~~~
.,
Figure 7.23: Target response of the two metal grid targets, being the small and larger grid reflector, spaced 15 cm apart in range.
, RMg_JmI
(a)
~ f o.j-----..J
(b)
Figure 7.24: The processed target response using inverse filtering with (a) reel window (b) Hanning window. Two targets are in the scene, placed 15 cm apart in range.
92
7.3.4 UWB Phased Array Beamforming
As mentioned in Section 7.3, four Vivaldi PCB antennas, spaced at 15 em, are used as
the receiving antennas in the UWB array radar. The background profiles and reference
signal profiles were captured at the start of the experiment. Since each receiving antenna
has a slightly different antenna characteristic, therefore, each antenna has a different set
of background profile and reference signal profile. Thereafter, the two metal grid targets
were placed in the scene. Figure 7.25 shows the position of the antennas and the targets.
Target 1 and Target 2 labeled on Figure 7.25 are the small metal grid and the large metal
grid respectively (descriptions in Table 7.1).
Array Formation and Tclrget Placement 6~~----~--~-----r----~----r---~~
, , . , , , , , , ,
5 · .... t· ...... · .... r·· .. ·' .. · .. · .. (··· .... ·· .. j"' ...... · .... ~·· .... ·· .... ·~····· .. ·, .... ·t .. · .. , , , . . , , • , , , • > • , , , . . , ,
4 ....... i"~" "."' .. "' .. ~,+. ~~ ........ ~. ""1'" .. ~~ ..... ~.~~ ~~ .. ~~ .. ~ ~ .... "~~f'~' ~ .-..... -.... 19 •••• ~ ... ~- ••• ~f· ..... .
! : t Target 2 j ~ ; ;
I :I.·1...·[[I..1.11 : : :)(: : Target f :
1.:~~~~~~~,EI':"~"~l~ld ......................... : .... . ! : ~ 1 2:3 4 ~ ! ; o ................................... " ... , ............... , .. " ....................... , ..
] Tra~smitter 1 i t [
-1 '---=.]=-----."='2-----=.1-:-----O=-------=1-----2t----=3----' IC-GridtmJ
Figure 7.25: Position of the radar and the targets.
Inverse filtering with a Hanning window was used to process the raw target responses.
Figure 7.26 shows the processed target responses for all the four receiving channels.
Thereafter, the filtered responses were basebanded, and beamforming process with Han
ning aperture weighting was perfonned. Figure 7.27 compares the fan-beam images,
which are generated using (a) simulation and (b) captured data set. Although the image
is smeared due to the noise from the scene and receiving circuit and the limitations of the
calibration process, the location of the targets shown in the image is close to the actual
position of the target.
7.3.5 Through Wall Detection - Wall thickness
When an electromagnetic wave enters a medium of a different reflectivity, some of the
signal is reflected. Hence, when a UWB signal travels through a wall, two reflections oc-
93
I
!L-l~_. __ ..
..~ .
. .
I i _.j"'-. ___ _
--- , .. ~ .
~ IgllI'C 7_ 20 : n", pr\'",:1.".,d IMg(1 ~'lOn'-C ,.f" u ' /Th'U1 Jrid •• I n ... , aU r«e" "'t ~ k.I/"I~1.
1m en;e ~ heri!)!! ,,;In Ibll""'11 .... ",do" j, u_'>fil (ur siV131 ptOl:C'nill@. .
•
• ! -.-•• . "
hs.u~ i.~1: I an·l:>eam ima£~ "fdoe Sl"CTIe j:( lIerntcd u~iD!! 13) SlmulalWll (1:» C.r.pI uI\'d \boll! , .... Tho: ~"ne L"'lfI>.i~" "r . .... u ,,,,"(al grid r 'ckl uf' i~" - 8 .. 1"
"
;:ur: 3,); the ,ignal emcrs the \\all ullda.'; the signal ", it s the ..... alL By finding the ~;'(;]'K~
between Ihe t"o rcilection. the thidtncss ,.1" the wall can b<: obtain,·d.
III the pnoyi,.u, npcrim<"!,t. a hac ~ ;:""ulI,j Im,j , k. "hid, i~ rrC'(" () f lhe la'!;<:I. i~ c"ptu~d
al the ,lal1 "fthe eXJ'C,;mCII'. II i, ,"hl"'~t~,i j",,,, 'he "'" !>I,);", n"["1n,,, 1(\ ..,Hallhe
1''';;l1 si~""luno I""" bac:,\:n'und dulll'''. H,'"<",,cr. Ihe largcHII"l<:l-(lcl~li()" tiu thi,
np",i"'cnt i, lh~ hrid "all. "hid, c~n mIl t><: Tcn~"e i,,,,,, the ~(~,,~ . ilen,"e. th" I'd"
1''';;''1 n."p<)I"e "r Ihe b"c~ wall. willi, 'UI n;:,n", illg (he hH~~llrm.md d Ullcr. i, pr''''~''cd
~ir~cll~ "ith a refc",.l\;c ~i;:"HI,
Ih" ,ere","c~ si~nal ll~ed in Ihis e x~rjment i., lhe ~h() of Ih" small metal ~rid. The
thic kne s5 "fthe .... all un<kr (x~m l n~l i 0l11~ approx lmalely 3i5 cm. r;~u"'" ~ . ~8 ~hv\\'s
" pid",,, of Ihe hrick IIJIl ~nd the p!Dces.~ed target =pcons.: of lh( wall. usmg tn'-erse
filleTing. .... ith Ilanntn~ wlOdow.
J j ~,cm
, I
---,., rigur.: U 8: «s) riClur.: of Ihe brick .... all (b I processed target ~spon:5C of the "all. II",~= r.1l~ring "ilh H~lIJlin!: "ind<J" b u,~d IV P"-'ce~~ th~ la ~cl '''''1'0''''' .
I'rolf! Figu~ 7.28(b). the distance measured be\wecnlhe l"{l pea~ , is ""' 27 em. The ~fTor
betlleen lhe m~a.su....,d and Jetected thickness of lhe 11"<111. is du~ 10 the speed of pr(lpa·
galillfl in brick wall beill~ slower than the ,peed of pru~l!ati(ln in the ai r. Pn:scn ll}. the
d;'lanC~"<:l'''' ersiUl' HI);orithm u,~-d ;n (hi, th~,;s, has nvt ~d a~cwnled r"r Ihi, I"m~il ion,
7.3.6 Through \\",.III)('lcCli" n - I\. lo\·in g Targel
I hi' e, perin"'"t wa.<; (;(>"dlld~d w il h" trutc ,1" apl'iicHl iun of I 1','11 r"d~r im I'll' inl: 11'10_
Ijon Jel<'ctjoll
I he U\\ 0 arra~ <adar is I'lacw ill frunt "f lO ~ t m thl<:~ willI. "llGlt ~ w"l~inlt 1'L''''11t
,s !>ch,"", th,· wall. A ba<:kgn,und I'roli Ie "f tho: c>o.;cno: "" .. ......:vr<kd 01.1 tloe ~toll1 , .1 Ihc c.,·
penmclI!. Aftel'\, ,,rds. 11 p"fWn " as H>ltd IV "lllk lhrou~h II><: I'" ' .... ~ f'I!llC'"ctJly. "I"k
the ~spon!i<' of tht !i<'~ne "as ..... inJ; ",'<',>n!W rigure 7_2'1 iIIUW-"le< the I;t .... ''''1I) ano.!
vrocrahon i", oh ed in thIS t~imtnt .
•
,->S. 0 • •
• I , I-d'''~. ". 105cm tmc,k wa. ~ em ;
~ lIWBArray , •
ri~u~ 7.ZQ : The S,; luP l, l'll!I.· nj1Crimc<11 h" ,kll',I',,); nh'li'" , lio"'ugll,, III < .'" ~l'Icl ,,~II ,
Oll,e IQ'l;"1 rt'~I"'''~~ "n • .- .hl~LI",d h)' re!Oo,ing II", hack~ n...,nd clutier from Ihe re<;pon~
..,f th~ ~ccnc rt'co rJ .... 1. n",,\..'11 11,'1'. Si lV",1 11I\....,,,~~ i,,~ uoi liS "" e~ fi htring "iln II tlr\ning
"In oj"". ",,oj b<:p"","mill~ I'"-.ce<,,, 'Ih 3~"'" " .. ighung \\:1.< u.~ I,... proceos Ihe larS"1
rc<;p'msc Fil!\"'~ 7.,41 ,h",,"< ~ c()"~uli\"e '";a,,·1leam il1l~ge; Ihat .... ere recorded.
Th<.· ~'t"t is ~apl ural c.cry I"" .~",,,I< Ihc II"IlI i" I'mllau,...n In im~l!e updale rJle i~ due
I,. I"" ,In" I I'>I""n i ... ~,, ~, I'lIl e hel" c.:n microo;"nlrollu;lIId PC. , ia lhe: )l;""rial ron. r Ulure
' '''I''''' ''''>tll l can t>t m.do: u5ing n I '<; n f"'I<1 for daL.1 1I· .. nsmi~ion. ri!;'u~ 1.30 Shll\"l
mal !he.- pO!;ilK>n and mo\cmcms ('f I person ~u" tic detec led . HI" ..... 'e'. lhe ~ "r lhe:
s~ "em i~ not fast enough 1<1 IH:ln(>ll'l ral,· ''''' ~'Ih ,,,,,Ii,,,, '"""',nlO nl a I'<'f'5I\<I " al L IIIS_
l"iJ,!urc ~how!i the )llmc dati bUI ",til IIa..Lg" ..... ,1d r rofile ",.:Iu.k.l . I h~t la.gel\ . ,e iden·
,ified in l'~(h fr,llllc;
fill-ure 7; 1 ,hoM thaI the rcHeelio" otra person and the rdl~ClIon orT Inc !i<'ctor«J brkk
"311 i~ milch 5'"Jllcr Ih.an Ihc rdlecli,...n nff the first bric k "ali. hellce ,n n~' st ,'asc) "f I-igun:: 7.J I. thc ad "al I"r~ct (the pcr .. ,n) cu" ,,,11 t>e clearly idenri l1cd nll~ i IluSI, UIC ~ Ihe
"1'l'Urt~'''-c uf t>;,d grourld·,,,111,.,..,1 j,l ,,·n Ig....-ilhm u~ in Ihj ~ Ihc~i,.
"
".
I ."
"
•
"
1<) framc'
F'!1~~ 7.3U, FJn·bc= jmJ~"'~ ID.''''ng a p""",n \, a l~i,,!.! ,;,,,,anJ Ihnlugh J pa~SlJ:\~
(rramn I.:> ,,"<.I 3). lh"" lumin~ :II"I,.'UI1o.1 in ItIt: middle ,.fbcam an'" "alli,,)! b~( l (f"'m("5 -I and ~ I. l·idJ ll f "i~" - 8../",
!
1>1 ~ .. _ I Ibl Fram.:
'~I FDm< ;
h .!O,,", 7 31 F~ ... ho: ... " .n""~~ <tJ,.'''lni; ~ p.:rS<1 n "allo..;n~ forv.ard lhrouph a P:OS$3j.:~ I tfllnK'S I. 2 and 3). tllen tum;n!' atQIJnd in tile miJdk Qf beam arJoJ ,,,.l ~il\,. ha(k (j;'.",,~~ 4 and ~) B".:kll""" ,,,,,ll'n, ti Ie ;, II,,, , ,,t>!,·a.:ted from lhe ra ... data. Field or, ie" • 84".
'l8
Chapter 8
Conclusions and Recommendations
1\ four .hannrl pnlscdllm) \.IWR r;l<l.lr ",.~~ de\'tI"J'I''' in sh;, ~i< 'n.,:. m"!I,...:h.~nnd
de ~' gn madl- IJ~ of optlmiu~ 'uh ·~~ :it"m C II'C U it.> fmm p< .... ,·i,~u , "nr~', "',,'<'011 .nll"" '·~'
mrn!! ..... re mJdr:
• The ampl i,mJ,c of (I", lrlln,m iued s j~aJ is im:n:aSl'd by u~ing an inlttd, !(Jtal cap.loC l·
Ie" ~:j 11k ~h~r~it\K Cipr., .. ;,or lllC inlwJil(i,,,1 tHpOC ilOr thai was huill In lhi. th~,is.
hi" a *",ncr h'~ f[l.·'luen.:~ 1'1:'1>'''''>'' than Ih .. · ~h,p u.pac ilox. ;.~. J nall~r rreq~n<:>
"';pM'" t...1"'''~'nI I (j, 11 alld -l ()H ~ "ltll .l . ~6 dB lo<;s
• I M US~ " r ~ rr~:unmobl.: Jo,I~) ,i,.,., cnhB"".,J lh. tkl<o)' ~oolriJl a"d :I,:~"r:K")'
u~J In ,he- IflIC'!V"III1¥ ...mlp ler.
• r" u ~nll .. ,¥ .", ItdlK _ u~J II! Ji .. clurg. lhe iGtogr31ing capac ,I OH ,ha, arc used in
Ihe inlq,m,' ;ng lI'unpll'f. The M31.J.J! S" itell<:. can dl~~.lIfl!. !he Inlt!lrahng eapa.: ,,,,,
Ith'''' "m,-w n' l~ tkin \ho.' JU' i<ltd dc:;ign This increa.;es :he m:I.~Im"m 5v.ecr r J lt
... n lle '~>I~rn i>l" a rae.,,.. or 10
• rho: " sate •• 1 .1 ~'v.-" nl."e m icrov.:we ampllfrer impr"'·c.J .t..- 'iNR or ,"'" ""''';, ... , ,~ <. ~m .
• TIlr.; II" ' !!" <Ir K m icroconll(llk.- inlegralC"d the f1iW S~"Sltm, " h,d. i~ 00""'" ~ , rq>
,'Iu.er Iv a port""'~ ~~ S1em"
• A (;111 "J' do", ckrpcd I" in~ I Or I'; thc'<l pn'grummi,,~ l:mgUJ~". "hkh Jlluv. 5 the
U-CI1(l ~"n\lnlllwt '~.Len.
the '~~1r"n J" " I~"111,HI (:IC "ll l h~ r\<"W UWR r"Jar " "S m~asured and an:ll) led From I~
resu lt s l'IfeM' nL~d In ~cCLinn 7.~. n """ I>e toncludcd 111., Ihe III'" '~'lclll hA S M imprO'< ed
perfum1lln(e in I trm~ or $ubilny and ~ ~ IC
L'I"'rnncnls ,,~ ... C~ ... JucleJ 10 ill u,Mat" Ur<' f""Ssibk appli(mioth f,1/ I I \\ II .11 I ~"\ m.!."
I h~ .... In~ lua.:
• Detecting various targets with a different geometry.
• Detecting objects through an obstruction.
• Movement detection through an obstruction.
From the result shown in Section 7.3, it can be concluded that UWB radar system is ideal
for detecting objects in short range applications, as the fine range resolution enables the
radar to resolve closely-positioned targets. Furthermore, this UWB radar has shown its
ability to perform through-wall imaging and detect a human walking behind a brick wall.
Overall, an integrated UWB phased radar has been developed. It can be used to detect
objects and movement of metallic and non-metallic targets.
Future work should include
• Develop a battery power supply for the UWB radar system. This would allow a true
portability of the radar system.
• Additional research into methods of increasing the pulse amplitude to further im
prove the detection of weak targets.
• A full investigation on UWB beamforming algorithm should conducted. This sim
ulation should demonstrate the differences in beam pattern and grating lobe effects
between a UWB and a narrow-band system.
• Develop a USB interface for higher data rate transmission between the microcon
troller and computer.
• If a longer range profile is required, the potentiometer that is used to control the
second post gain stage (TL092), can be replaced by a programmable potentiometer
for a better user control.
• Investigating of the system in various applications (GPR, through-wall etc.)
100
Appendix A
Ultra-Wideband Circuit Schematics
Figure A.I: UWB transmitter circuit diagram
101
~ -:r.>O r ,a~aa I'tI ,az,s l~tr.:J..J1::J ....ta<I!.~J ptR!C¥IP!,...-B.J11fl dB("l~1.
lard
-.1:'M"IIiUd....,,~
! tI:I :.a .... _ ........ ,""
" 'S ~ .g (,)
t .~
N U ! (,) 0
U -u-"'L!' l'l-l '"'
~ N « a
u::
AppendixB
Nyquist Theorem for Bandpass Signal
The material presented in this appendix was adopted from [21].
Consider a signal of bandwidth B, centred on 10 = 1.SB, as shown on the left of Fig
ure B.1(a). If the signal is sampled at Nyquist sampling frequency for low-pass signal,
which is Is = 21max = 2 x (2B) = 4B, the spectrum of the sampled signal will have some
unoccupied space, as depicted on the right of Figure B.1(a).
In the case of reducing the sampling frequency to Is = 2B, the result indicates that there is
no overlap in the spectrum of the sampled signal, as depicted on the right of Figure B.1 (b),
which suggested that the original signal could be recovered from it.
Signal.!!8.111pled at Is 21 rrw.:r = 4B
1 B
1 B ....... -;N\ /P\ h?\ ~\ MM fA
B t 2B
/fi I .. = 2/moz
Signal sampled at Iii = 2B
1 B
~h\ -G\ A .. B 2B B 2B
Figure B.1: Frequency domain representation of sampled bandpass signals [21].
However, if the centre frequency of the signal is reduced slightly, the sampling frequency
of Is = 2B will not be sufficient as the replicas of the signal spectrum will not fit the gaps
without overlapping with each other. In this case, the signal is required to be sampled at
twice of the highest frequency component of the signal.
103
For a bandlimited signal, the Nyquist sampling frequency fNyquist changes as the lowest
frequency component of the signal/L increase. Figure B.2 shows the relationship between
them (both expressed in terms of B).
4B
2B
B 2B 3B 4B 2B
Figure B.2: Graph showing the relationship between the Nyquist frequency and the lowest frequency component of a bandlimited signal. Both frequency are expressed in terms of B, which is the bandwidth of the signal [21].
104
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