Seminar Report on UWB FM -CW RADAR
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Transcript of Seminar Report on UWB FM -CW RADAR
A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
Abstract
Today world is going very fast in
terms of technology, and triggering to latest
technologies, one of the technologies
evolved far back is detecting humans, the
detection of human beings is done in various
ways like Imaging Techniques, Sensing
Techniques, both the imaging and sensing
techniques will work when the human is in
front of the equipment or the machine, the
disadvantage of the imaging and sensing
techniques can’t detect humans behind the
obstacle, this disadvantage evolved to detect
human beings behind the walls or obstacles
this can be achieved using RADAR. We
know that Radar is conventional and
commercial equipment that had been serving
for different purposes in different ways, the
working nature of radar helped to improve
the security more by introducing the latest
technology i.e, through the wall human
detection.
The technology through-the-wall
(TTW) radar demonstrator for the
detection and the localization of people in a
room (in a no cooperative way) with the
radar situated outside but in the vicinity of
the first wall. After modeling the
propagation through various walls and
quantifying the backscattering by the human
body, an analysis of the technical
considerations which aims at defining the
radar design is presented. Finally ultra
wideband (UWB) frequency modulated
continuous wave (FMCW) radar is
proposed, designed, and implemented. The
FM-CW Radar with an extended frequency
sweep form 0.5 to 8 GHz is presented it has
been applied to the TTW human detection.
Some representative trials show that this
radar is able to localize and track moving
people behind a wall in real time. This
Radar will enable large stand-off distance
capabilities and in depth building detection.
1. INTRODUCTION
Here we assess human detection through
the wall using UWB (Ultra Wide Band)
radars, we know that radar stands for radio
detection and ranging, i.e, using RADAR we
can find the Range, Direction and angle of
the object, radar uses electromagnetic waves
that are transmitted by the transmitter into
the air to detect the object or reflecting
material, the reflected echo signal from the
object must be in the direction of the
Receiver to find the range, there are
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
different types of radars have been
developed for different applications
The detection of humans hidden by walls
or rubble, trapped in buildings on fire or
avalanche victims are of interest for rescue,
surveillance and security operations. The
problem of rescuing people from beneath the
collapsed buildings does not have an
ultimate technical solution that would
guarantee efficient detection and localization
of victims. The main techniques used are:
Cameras with long optical fibers that are
injected into the holes or fissures in the
collapsed buildings (the usability of such
devices and their efficiency depend on the
structure of collapsed building and besides,
when the victim is detected it is difficult in
the most cases to determine its actual
position). Sledge hammers are used to give a
signal to potential victims, and rescuers with
microphones are waiting for hearing the
response (obvious limitation of this method
is that unconscious people cannot be
detected. Localization of victims is a
problem as well). Search dogs are deployed
in the disaster area. They detect presence of
victims efficiently by smell, but information
about their actual positions or quantity
cannot be indicated. Moreover, dog is likely
to indicate the presence of dead person
which distracts rescuers from locations
where living people can still be found [1].
Due to the ability of electromagnetic waves
to penetrate through typical building
materials and its significant (in order of
centimeters) spatial resolution, UWB radar
is considered as preferred tool for detection
and localization of people. Detection of
human beings with radars is based on
movement detection – respiratory motions
and movement of body parts. These motions
cause changes in frequency, phase,
amplitude and periodic differences in time-
of-arrival of scattered pulses from the target,
which are result of periodic movements of
the chest area of the target [2].
Typical radar applications are listed here to
give an idea of the huge importance of
radar in our world.
Surveillance
Military and civil air traffic control, ground-
based, airborne, surface coastal,
satellitebased
Searching and tracking
Military target searching and tracking
Fire control
Provides information (mainly target
azimuth, elevation, range and velocity) to a
firecontrol
system
Navigation
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
Satellite, air, maritime, terrestrial navigation
Automotive
Collision warning, adaptive cruise control
(ACC), collision avoidance
Level measurements
For monitoring liquids, distances, etc.
Proximity fuses
Military use: Guided weapon systems
require a proximity fuse to trigger the
explosive
warhead
Altimeter
Aircraft or spacecraft altimeters for civil and
military use
Terrain avoidance
Airborne military use
Secondary radar
Transponder in target responds with coded
reply signal
Weather
Storm avoidance, wind shear warning,
weather mapping
Space
Military earth surveillance, ground mapping,
and exploration of space environment
Security
Hidden weapon detection, military earth
surveillance
Through The Wall (TTW) human
detection using radar is a relatively new
topic that has been investigated in many
countries all around the world. It addresses
the ability to see behind walls in order to
detect, count, and localize people inside a
building. We would like to remain at large
stand off distances (5-10 or even 50 m) if
possible, according to the allowed emitted
power. TTW Radars utilize frequencies
ranging from UHF to S band in order to
have better wall penetration for any kind of
wall. It is further more recommended to use
ultrawideband (UWB) modulations in order
to achieve range resolution for human
localization and to deal with indoor
propogation channel. Through-the-wall
(TTW) radar technique addresses
electromagnetic “vision” behind walls in
order to detect, count, and localise people
inside a building. Considering one by one
these three objectives: detect, count, and
localise, it is possible to situate our work
among the various researches that are
ongoing in the TTW radar field.In order to
detect one or more persons in a room, it is
necessary to take into account the fact that
these people move. In fact, the radar return
coming from the human body is not high
enough compared to the backscattering of
the indoor environment to ensure detection.
So that, Doppler effect has been used
historically to detect motion through walls
[1]. Nevertheless, Doppler radar has also
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
some drawbacks. The first one is its high
sensitivity to all kinds of motions bringing
false alarms. The second one is that target
localisation and Doppler filtering seems
incompatible. This is why emphasis was
made on imaging radar with the ability to
count and localise targets.Small TTW radars
based on the technology of UWB pulses
appeared since the 2000s. The famous ones
are Radarvision and then Xaver by
CAMERO. There is no publication about
them in the open literature. Besides, some
radar and signal processing specialized
laboratories have studied UWB radar
imaging or SAR imaging applied to through-
wall vision [2, 3].The work presented here
gives the last advances from our laboratory
in the “see-through” radar topic. It aims at
giving a global approach of the TTW radar
detection. It shows step by step the design
process after radar modelling: from
theoretical background to radar realization
followed by experimental assessment.
In Section 2, the through-the-wall
propagation physics has been studied by
simulation and also assessed by
measurements. Then, in Section 3, the
backscattering strength of the human body is
quantified in an anechoic chamber with
various people under test. Section 4 is
centred on an analysis of technical
considerations which aims at defining the
best radar design. And finally, Sections 5
and 6 present the radar implementation and
a trial of people detection and localization
through a wall.
So many radars have been developed to
detect ranges of any distinct object, the
various radars are
1. Pulsed Doppler radar
2. Continous wave radar
3. FM-CW radar
4. MTI Radar
5. Phased Array Radar
6. Synthetic Aperture Radar
7. Bi Static and Multi Static radar
8. Passive Radar
9. Multimode Radar
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
2. Literature Survey
Before moving into the different types of
radars used for different applications, let’s
check the radar frequencies, Bands,
Wavelengths and its applications.
2.1. Radar Frequencies, - Bands, Wavelength and Applications
Band
Frequency
Wavelength
Application
HF
3-30 Mhz
10m-100m
Coastal radar systems, over-the-horizon (OTH) radars; ’high frequency’
P 30 to 300 Mhz
1m to 10 m
’P’ for ’previous’, applied retrospectively to early radar systems
UHF
300-1000Mh
z
0.3-1m Very long range (e.g. ballistic missile early warning), ground
penetrating, foliage penetrating; ’ultra high frequency’
L 1 – 2 GHz
15 cm to 30 cm
Long-range air traffic control and surveillance; 'L' for 'long'
S 2 – 4 GHz
7.5 cm to 15 cm
Terminal air traffic control, long-range weather, marine radar; 'S' for 'short'
C 4 – 8 GHz
3.75 cm to 7.5 cm
Satellite transponders; a compromise (hence 'C') between X and S bands; weatherradar
X 8 – 12 GHz
2.5 cm to 3.75 cm
Missile guidance, marine radar, weather, medium-resolution mapping and ground surveillance; in the USA the narrow range 10.525 GHz ± 25 MHz is used for airport radar. Named X band
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
because the frequency was kept secret during World War 2.
KU 12 – 18 GHz
1.67 cm to 2.5 cm
High-resolution mapping, satellite altimetry; frequency just under K band (hence 'u')
K 18 – 27 GHz
1.11 – 1.67 cm
K band is used by meteorologists for detecting clouds and by police for detecting speeding motorists. K band radar guns operate at 24.150 ± 0.100 GHz. Automotive radar uses 24 – 26 GHz.
Ka 27 – 40 GHz
0.75 cm to 1.11 cm
Mapping, short range, airport surveillance; frequency just above K band (hence 'a'); photo radar, used to
trigger cameras that take pictures of license plates of carsrunning red lights, operates at 34.300 ± 0.100 GHz
Mm 40 – 300 GHz
1 mm to 7.5 mm
Millimeter band, subdivided as below. The letter designators appear to be random, and the frequency ranges dependent on waveguide size. Multiple letters are assigned to these bands by different groups
Q 40 – 60 GHz
5 mm to 7.5 mm
Used for military communications
V 50 – 75 GHz
4 mm to 6 mm
Very strongly absorbed by the atmosphere
W 75 – 110 GHz
2.7 mm to 4 mm
76 GHz LRR and 79 GHz SRR automotive
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
radar, high-resolution meteorologicalobservation and imaging
2.2. Radar Equation
The acronym RADAR stands for Radio Detection And Ranging. Figure 1 shows the basic principle.
Figure 1: Basic principle of Radar and its parameters
An electromagnetic wave of power Pt is
transmitted to a flying object, for example to a
plane and is partly reflected back to the antenna
with the receiving power Pr. From the time
delay between the transmitted and received
signal the distance to the plane can be
calculated. Additional information can be gained
from the frequency shift of the received signal,
which is proportional to the speed of the plane.
Receiving a signal of sufficient power by an
adequate power to noise ratio is the biggest
challenge of radar systems. The so called .Radar
Equation. gives hints on the power relations
within the system as indicated in Figure1. The
Radar Equation delivers the received power Pr
as result. According to the Radar Equation
following independent parameters determine the
received power Pr.
Pt: The power transmitted by the antenna,
dimension is dBm. Numeric examples : 63
dBm for real world Radar applications, 13
dBm for laboratory tests
G: Gain of the transmitting antenna,
dimension in dBi. The parameter determines
how much the radiation beam of the antenna
is focused toward the direction of the target.
Numeric examples are 12 dBi for a BiQuad
antenna and 70 dBi for a highly focusing
parabolic antenna.
σ is The wavelength of the transmitted
signal, dimension in meter. The wavelength
can be directly calculated from the
frequency. Numeric examples: 0.03 m for a
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
10 GHz signal and 0.12 m for a 2.54 GHz
signal
Radar cross section, RCS, is a virtual area
representing the intensity of the reflection.
Not all of the radiated power is reflected
back to transmitting antenna, as indicated by
the small waves close to the plane in Figure
1. The .Sigma. ( ) of the objects determines
the virtual area of the reflecting object
(plane) from which all of the incoming
radiation energy is reflected back to the
antenna. The dimension is square
meter, .m2. in short. Practical examples are
12 m2 for a commercial plane, 1 m2 for a
person or 0.01 m2 for a bird. Refer to [18],
page 6665 for further
examples.
R: Distance between the transmitting
antenna and the reflecting object. Dimension
in m. Numeric examples are 8000 m for real
world applications or 5 m for laboratory
conditions. It has to be stressed that this
parameter reduces the result, i.e. the
received signal by the power of 4, with the
effect that far distant objects are providing
only a small amount of received power.
Table 1: Parameters of Radar Equitation and two
examples
Parame
ter
Abbrevi
ation
Value
,
Exam
ple 1
Value
Exam
ple 2
Uni
t
Transm
itted
power
Pt 63 13 dB
m
Gain of
transmi
t
antenna
G 28 12 dBi
Wavele
ngth
(freque
ncy)
(f) 0.03
(10*1
09)
0.12
(2.5*1
09)
m(
Hz)
Radar
cross
section
12 0,3 m2
Distanc
e
R 8114 5 m
Receive
d
power,
linear
Pr 1 17.4*
103
pW
Receive
d
power,
logarith
mic
Prlog -90 -48 dB
m
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
Example 1 shows a a real world example,
derived from [Pozar], example 2 shows a
radar application which can be realized
under laboratory conditions for example
in an anechoic chamber.
Example 1 read in clear text : A radar
transmitting antenna with gain of 28 dBi is
transmitting an electromagnetic wave at 10
GHz with a power of 63 dBm to a plane in a
distance of about 8000 m. The plane has a
radar cross section of 12 m2 . By means of
the Radar Equation the received power back
at the antenna is calculated to -90 dBm.
Example 2 read in clear text: In a radar test
laboratory implemented in an anechoic
chamber a test transmitter provides 13 dBm
to a matched antenna of 12 dBi with a
frequency of 2.5 GHz. The reflecting object
with a cross section of 0.3 m2 is located in 5
m distance from the transmitting antenna.
According to the Radar Equation the test
receiver is going to receive a reflected signal
of -48 dBm.
When comparing example 1 to example 2
we can conclude that despite much bigger
transmitting power, better transmit antenna
gain and bigger radar cross section in
example 1 the received reflected power of
example 1 is almost 50 dB lower than the
received signal of example 2. The reason is
the smaller wavelength lambda which
affects the result by a power of 2 and
especially the bigger distance R of example
1 which affects the result by a power of 4.
Small wavelengths, i.e. high frequencies are
aimed for in most radar systems, especially
in antenna arrays, because of the resulting
small antenna size. It is obvious also, that in
radar technology one has to deal with very
small receiving power especially for far
distant objects.
2.3. Common Radar types for
Common Applications
2.3.1.Simple Pulse (Range) and Pulse Doppler (Speed/Range)Radar
Basic principle of a simple pulse radar system
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
A simple pulse radar system only provides
range (plus direction) information for a
target based
on the timing difference between the
transmitted and received pulse. It is not
possible to
determine the speed. The pulse width
determines the range resolution.
Direction information with azimuth angle determination in a radar system with a rotary
antenna
The direction information (azimuth angle) is
determined from the time instant of the
receive pulse with reference to the
instantaneous radiation direction of the
rotating antenna. The important
measurements on (non-coherent) radar
equipment of this sort are the range accuracy
and resolution, AGC settling time for the
receiver, peak power, frequency stability,
phase noise of the LO and all of the pulse
parameters.
The AGC circuit of the receiver
protects the radar from overload conditions
due to nearby collocated radars or jamming
counter measures. The attack and decay time
of the AGC circuit can be varied based on
the operational mode of the radar. Since the
roundtrip of a radar signals travels
approximately 150 meters per microsecond,
it is important to measure the response of the
AGC for both amplitude and phase response
when subject to different overload signal
conditions. The measured response time will
dictate the minimum detection range of the
radar.
Pulse Doppler radar
A pulse Doppler radar also provides
radial speed information about the target in
addition to range information (and direction
information). In case of coherent operation
of the radar transmitter and receiver, speed
information can be derived from the pulse-
to-pulse phase variations. I/Q demodulators
are normally used. The latest pulse Doppler
radar systems normally use different pulse
repetition frequencies (PRF) ranging from
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
several hundred Hz up to 500 kHz in order
to clarify any possible range and Doppler
ambiguities. More advanced pulse Doppler
radar systems also " use "staggered PRF, i.e.
the PRF changes on an ongoing basis to get
rid of range ambiguity and reduce clutter as
well. Important criteria for achieving good
performance in pulse Doppler radar systems
include very low phase noise in the LO, low
receiver noise and low I/Q gain phase
mismatch (to avoid "false target indication")
in addition to the measurement parameters
listed above. When measuring the pulse-to-
pulse performance of a radar transmitter, it
is important to understand the variables that
can impact the uncertainty of the
measurement system for accurate Doppler
measurements:
Signal-to-noise ratio of the signal -
the better the signal to noise ratio of
the signal, the lower
the uncertainty due to noise
contribution.
Bandwidth of the signal - the
bandwidth of the IF acquisition
system must be sufficient to
accurately represent the risetime of
the pulsed signal, however too much
bandwidth can
result in added noise contribution
uncertainty.
Reference (or timebase) clock
stability.
Jitter or uncertainty due to the
measurement point of the rising edge
of the signal . rising edge
interpolation or signals that have
changing edges impact this
uncertainty.
Overshoot and preshoot of the rising
and falling edges . any ringing on the
rising and falling edges can impact
the measurement points adversely on
a pulse to pulse basis. It is important
that the measurement point, or the
average set of measurement points,
are sufficiently far
away in time from the leading and
falling edges of a pulse. Applying a
Gaussien filter to smooth the impact
of the rising and falling edges can
reduce this phenomena and is often
implemented in the Doppler
measurement system of a radar
receiver.
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
Time between measured signals . due
to the PRI of the measured signal,
the close-in phase noise of the
measurement system needs to be
considered due to the integration
time at lower offset frequencies.
The same variables can also
contribute to the uncertainty in the
signal generator when testing the
receiver circuit and Doppler
measurement accuracy.
Continuous Wave (CW) Radar:
A continuous wave (CW) radar
system with a constant frequency can be
used to measure speed.However, it does not
provide any range (distance) information. A
signal at a certain frequency is transmitted
via an antenna. It is then reflected by the
target (e.g. a car) with a certain Doppler
frequency shift. This means that the signal’s
reflection is received on a slightly different
frequency. By comparing the transmitted
frequency with the received frequency, we
can determine the speed (but not the range).
Here, a typical application is radar for
monitoring traffic.
Radar motion sensors are based on the same
principle, but they must also be capable of
detecting slow changes in the received field
strength due to variable interference
conditions that may exist.
Radar speed traps operated by the
police use this same technology. Camera
systems take a picture if a certain speed is
exceeded at a specified distance from the
target.
Mobile traffic monitoring radar
MultaRadar CD - Mobile speed radar for speed
enforcement from Jenoptic
There are also military applications:
CW radars are also used for target
illumination. This is a straightforward
application: The radar beam is kept on target
by linking it to a target tracking radar. The
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
reflection from the target is then used by an
antiaircraft missile to home in on the target.
CW radars are somewhat hard to detect.
Accordingly, they are classified as low-
probability-of intercept radars.
CW radars lend themselves well to
detecting low-flying aircraft that attempt to
overcome an enemy’s air defense by
"hugging the ground". Pulsed radar has
difficulties in discriminating between
ground clutter and low-flying aircraft. CW
radar can close this gap because it is blind to
slow-moving ground clutter and can
pinpoint the direction where something is
going on. This information is relayed to co-
located pulse radar for further analysis and
action. [7]
The disadvantage of CW radar is that
it cannot detect the Range due to Narrow
Bandwidth of the transmitted signal, to
measure the range we are moving forward to
the Frequency modulated transmitted signal,
which can be used to find the range of ay
distinct object.
FM-CW Radar ( Frequency
Modulated – Continuous Wave)
The disadvantage of CW radar
systems is that they cannot measure range
due to the lack of atiming reference.
However, it is possible to generate a timing
reference for measuring the rangeof
stationary objects using what is known as
"frequency-modulated continuous wave"
(FMCW) radar. This method involves
transmitting a signal whose frequency
changes periodically. When an echo signal
is received, it will have a delay offset like in
pulse radar. The range can be determined by
comparing the frequency. It is possible to
transmit complicated frequency patterns
(like in noise radar) with the periodic
repetition occurring at most at a time in
which no ambiguous echoes are expected.
However, in the simplest case basic ramp or
triangular modulation is used, which of
course will only have a relatively small
unambiguous measurement range.
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
Basic principle of FMCW radar. The target’s velocity is calculated based on the measured delay
tbetween the transmit signal and the received
signal, whereas the frequency offset f gives the
range
This type of range measurement is
used, for example, in aircraft to measure
altitude (radio altimeter) or in ground
tracking radar to ensure a constant altitude
above ground. One benefit compared to
pulse radar is that measurement results are
provided continuously (as opposed to the
timing grid of the pulse repetition
frequency). FMCW radar is also commonly
used commercially for measuring distances
in other ways, e.g. level indicators.
Automotive radar is in most cases FMCW
radar too
Moving-Target Identification (MTI)
Radar
The idea behind MTI radar is to
suppress reflected signals from stationary
and slow-moving objects such as buildings,
mountains, waves, clouds, etc. (clutter) and
thus obtain an indication of moving targets
such as aircraft and other flying objects.
Here, the Doppler effect is exploited, since
signals reflected by targets moving radially
with respect to the radar system exhibit an
offset vs. the transmitted frequency which is
proportional to their speed (e.g. in linear FM
radar).
In pulse radar systems, the pulses
reflected by moving objects have a variable
phase from pulse to pulse referenced to the
phase of the transmitted pulses.
3. UWB RADAR
Technology
Ultra Wideband technology has been an
extremely evolving technology because of
its appealing characteristics like achieving
high data rates, more capacity as compared
to narrowband systems, and co-existence
with the existing narrowband wireless
technologies. A signal is categorized as
UWB if its bandwidth is very large with
respect to its center frequency. That results
that the fractional bandwidth should be very
high. The FCC defines UWB as a signal
with either a fractional bandwidth of 20% of
the center frequency or 500 MHz (when the
center frequency is above 6 GHz). The
formula proposed by the FCC commission
for calculating the fractional bandwidth is
[3, 4]: Where fH represents the upper
frequency of the -10 dB emission limit and
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
fL represents the lower frequency limit of
the -10dB emission limit
UWB is based on the generation of very
short duration pulses of the order of
picoseconds. The information of each bit in
the binary sequence is transferred using one
or more pulses by code repetition. This use
of number of pulses increases the robustness
in the transmission of each bit. In
UWBcommunications there is no carrier
used and hence all the references are made
with respect to the center frequency. In Ultra
wideband communications, a signal with a
much larger bandwidth is transmitted with a
reduced power spectral density. This
approach has a potential to produce signal
which has higher immunity to interference
effects and improved time of arrival
resolution. Ultra wide band communications
employ the technique of impulse radio.
Impulse radio communicates with the help
of base band pulses of very short duration of
the order of nanoseconds, thereby spreading
the energy of the signal from dc to few
gigahertz. The fact that the impulse radio
system operates in the lowest possible
frequency band that supports its wide
transmission bandwidth means that this
radio has the best chance of penetrating
objects which become opaque at higher
frequencies. Impulse radios operating in the
highly populated frequency range below a
few gigahertz must contend with a variety of
interfering signals. They must also guarantee
that they do not interfere with the narrow-
band radio systems operating in dedicated
bands. These requirements necessitate the
use of spread spectrum techniques. A means
of spreading the spectrum of the ultra-
wideband pulses is to employ time hopping
with data modulation accomplished by
additional pulse position modulation at the
rate of many pulses per data symbol. The
use of signals with gigahertz bandwidth
means that multipath is resolvable down to
path differential delays on the order of
nanoseconds or less i.e. down to path length
differentials on the order of foot or less. This
significantly reduces fading effects even in
indoor environments. The advantages of
UWB over conventional narrowband
systems are [3]:
Large Instantaneous bandwidth that
enables fine time resolution for
network time
distribution, precision location
capability, or use as a radar.
Short duration pulses that provide
robust performance in dense
multipath
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
environments by exploiting more
resolvable paths.
Low power spectral density that
allows coexistence with existing
users and has a
Low Probability of Intercept (LPI).
Data rate may be traded for power
spectral density and multipath
performance
3.1Salient Features of Ultra-wideband Radars
3.1.1 High Data rate
UWB can handle more bandwidth-
intensive applications like streaming video,
than either 802.11 or Bluetooth because it
can send data at much faster rates. UWB
technology has a data rate of roughly 100
Mbps, with speeds up to 500 Mbps, This
compares with maximum speeds of 11 Mbps
for 802.11b (often referred to as Wi-Fi)
which is the technology currently used in
most wireless LANs; and 54 Mbps for
802.11a, which is Wi-Fi at 5MHz. Bluetooth
has a data rate of
about1Mbps.
Maximum range and data rate of different
wireless technologies
Low power consumption
UWB transmits short impulses
constantly instead of transmitting modulated
waves continuously like most narrowband
systems do. UWB chipsets do not require
Radio Frequency (RF) to Intermediate
Frequency (IF) conversion, local oscillators,
mixers, and other filters. Due to low power
consumption,battery-powered devices like
cameras and cell phones can use in UWB
[3].
Interference Immunity
Due to low power and high
frequency transmission, USB’s aggregate
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
interference is “undetected” by narrowband
receivers. Its power spectral density is at or
below narrowband thermal noise floor. This
gives rise to the potential that UWB systems
can coexist with narrowband radio systems
operating in the same spectrum without
causing undue interference [3].
High Security
Since UWB systems operate below
the noise floor, they are inherently covertand
extremely difficult for unintended users to
detect [3].
Reasonable Range
IEEE 802.15.3a Study Group defined
10 meters as the minimum range at speed
100Mbps However, UWB can go further.
The Philips Company has used its Digital
Light Processor (DLP) technology in UWB
device so it can operate beyond 45 feet at 50
Mbps for four DVD screens [3].
Low Complexity, Low Cost
The most attractive of UWB’s
advantages are of low system complexity
and cost. Traditional carrier based
technologies modulate and
demodulatecomplex analog carrier
waveforms. In UWB, Due to the absence of
Carrier, the transceiver structure may be
very simple. The techniques for generating
UWB signals have existed for more than
three Decades. Recent advances in silicon
process and switching speeds make UWB
system as low-cost. Also home UWB
wireless devices do not need transmitting
power amplifier. This is a great advantage
over narrowband architectures that require
amplifiers with significant power back off to
support high-order modulation waveforms
for high data rates [3].
Large Channel Capacity
The capacity of a channel can be
express as the amount of data bits
transmission/second. Since, UWB signals
have several gigahertz of bandwidth
available that can produce very high data
rate even in gigabits/second. The high data
rate capability of UWB can be best
understood
by examining the Shannon’s famous
capacity equation:
𝐶 = 𝐵 log!(1 + !
!) (1.4)
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
Where C is the channel capacity in
bits/second, B is the channel bandwidth in
Hz, S is the signal power and N is the noise
power. This equation tells us that the
capacity of a channel grows linearly with the
bandwidth W, but only logarithmically with
the signal power S. Since the UWB channel
has an 19 abundance of bandwidth, it can
trade some of the bandwidth against reduced
signal power and interference from other
sources. Thus, from Shannon’s equation we
can see that UWB systems have a great
potential for high capacity wireless
communications [7].
Resistance to Jamming
The UWB spectrum covers a huge
range of frequencies. That’s why, UWB
signals are relatively resistant to jamming,
because it is not possible to jam every
frequency in the UWB spectrum at a time.
Therefore, there are a lot of frequency range
available even in case of some frequencies
are jammed.
Scalability
UWB systems are very flexible
because their common architecture is
software re-definable so that it can
dynamically trade-off high-data throughput
for range [6].
Application of UWB
Wireless technology is playing now
main role in our daily lives. In recent years,
demand of higher quality and faster delivery
of data is increasing day by day. The need of
more speed and quality brought up many
wireless solutions for short rang
communication. The family of Wi-Fi
standards (IEEE802.11), Zigbee
(IEEE802.15.4) and the recent standard
802.15.3, which are used for wireless local
area networks (WLAN) and wireless
personal area networks (WPAN), can’t meet
the demands of applications that needs much
higher data rate. UWB connection function
as cable replacement with date rate more
than 100 Mbps. Applications of UWB can
be categorized in following section.
Imaging Systems
UWB was firstly used by military
purpose to identify the buried installations.
In imaging system emission of UWB is used
as illuminator similar to radar pulse. The
receiver receives the signal and the output is
processed using complex time and
frequency functions to differentiate between
materials at varying distance. The lower part
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
of radio spectrum < 1 GHz have ability to
penetrate the ground and solid surfaces. This
property makes UWB a best choice for
detection of buried objects and public
security and protection organizations.
UWB plays an important role in
medical imagine and human body analysis.
Now a day’s ultra wideband radars are used
for heart treatment. All of inner body parts
of human being can be imaged by adjusting
the emitting pulse power [21].
Radar Systems
In early days military used UWB
technology in radar system to detect the
object in high-density media like ground, ice
and air targets. Research and studies in this
area found, radar can be used everywhere
where we need sensing of moving objects.
Radar systems can be installed in vehicle to
avoid accident during driving and parking.
UWB radars can be used in guarding
systems as alarm sensors to detect
unauthorized entrance into the territory.
These radars can be used to find objects or
peoples in collapsed buildings by detecting
the movement of person; but in case person
is not moving, it can still be detected by
heart beat and thorax beats. Police
department can use such radars to find
criminals hidden in shelters. These radars
are able to measure the patient’s cardiac and
breathing activity in hospitals as well as at
home [21].
Home Networks
In a home environment, variety of
devices are operating such as DVD players,
HDTVs, STBs, Personal video recorders,
MP3 players , digital cameras, camcorders
and others. The current popular usage of
home networking is sharing date from PC to
PC and from PCs to peripherals. Customers
are demanding multiplayer gaming and
video distributions in home network. These
all devices are connected using wires to
share contents at high speed. UWB is a wire
replacement technology provides high
bandwidth more than 100 Mbps. These all
devices can be connected in a home network
to share multimedia, printers, scanners and
etc. UWB can connect a plasma display or
HDTV to a DVD or STB without using any
cable. UWB also enables multiple streaming
to multiple devices simultaneously, that
allows viewing same or different content on
multiples devices. For example, movie
content can be shared on different display
devices in different rooms [1] [3]. The home
networks are directly connected to a
broadband through a residential gateway.
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
This approach is cost effective but is
ineffective for whole house coverage.
Cables are installed to connect different
devices with Internet in a home
environment. With a right UWB solution
Internet traffic from multiple users in a
home can be routed to single broadband
connection. UWB enable devices can be
connected in an ad-hoc manner like
Bluetooth to share contents. For example a
camera can be connected to a printer directly
to print pictures; MP3 player can be
connected to another MP3 player and shared
music.
Sensor Networks
Wireless sensor networks are an
important area of communication. Sensor
networks have many applications, like
building control, surveillance, medical,
factory automation etc. Sensor networks are
operated under many constraints such as
energy consumption, communication
performance and cost. In many applications
sensor size is also considered to be smaller.
UWB use pulse transmission, with very low
energy consumption. This property enables
us to design very simple transmitters and
thus long time battery operated devices.
These sensors can be used in locating
hospitals, tracking and communication
systems. These systems enable us to locate
and track objects including facilities,
equipment’s, nurses, doctors and patients in
a hospital [2]. Furthermore these systems
can be used in factories to track
equipment’s, employees and visitors.
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
The Future of Radar Developments
In the future, we can expect to
encounter multisensory systems that
combine radar and infrared (or other)
systems[11]. This will make it possible to
combine the benefits of the different types
of systems while suppressing certain
weaknesses [11].
Military onboard radar systems will
be increasingly confronted with the stealth
characteristics of advanced aircraft. The
contradiction between the different
requirements imposed on aircraft must be
solved (i.e. planes should exhibit stealth
properties while not revealing their position
through the use of onboard radar). One
possibility involves the use of a bistatic
radar system with a separate illuminator and
only a receiver on-board the aircraft.
In the future, radar antennas will in
many cases no longer exist as discrete
elements with suitable radomes. Instead,
they will be integrated into the geometrical
structure of the aircraft, ship or other
platform that contains them. The next
generation of AESA radars used on-board
aircraft will have more than one fixed array
in order to be able to handle greater spatial
angles.
Finally, the speed of the digital back-end
equipment handling the radar raw data will
need to
increase i.e. through parallel processing in
order to handle data rates as needed for high
resolution radar operating modes.[12]
REFERENCES
1. Merrill I. Skolnik,1990, Radar
Handbook, Second Edition McGraw-
Hill
2. Merrill I. Skolnik,1990, Radar
Handbook, Second Edition McGraw-
Hill, Chapter 7
3. http://www.radartutorial.eu/
index.en.html
4. http://www.radartutorial.eu/
rrp.117.html
5. http://de.wikipedia.org/wiki/
Synthetic_Aperture_Radar
6. http://keydel.pixelplaat.de/uploads/
File/vorlesung07-08/SAR.pdf
7. http://www.h2g2.com/
approved_entry/A743807
8. http://www.armedforces.co.uk/
releases/raq43f463831e0b7
9. http://www.pa.op.dlr.de/poldirad/
BISTATIC/index.html
10. Silent Sentry.Passive Surveillance
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A Study of UWB FM-CW Radar for the Detection of Human Beings in Motion Inside a Building
11. http://defense-update.com/
20110721_super-hornets-future-eo-
radar
12. radar-technology-looks-to-the-
future.html
13. http://www.radartutorial.eu/
06.antennas/an17.en.html
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