4. CONCLUSION
We have shown that the simultaneous logic gate operation
between half adder and subtractor can be formed by using the
dark-bright soliton conversion system via the add/drop optical
filter, which is formed by all-optical circuit using microring and
nanoring device structures, in which the advantage of the simul-
taneous logic gate operation between the half adder and subtrac-
tor arithmetic are seen. By using the dark-bright soliton conver-
sion system, the input data logic 0 (dark soliton) and logic 1
(bright soliton) is established, in which the logic status results
simultaneously at the drop- and through-ports, respectively. In
application, this device will be the great component to use for
digital photonic circuit design and recognized as the simple and
flexible system for logic switching system, which can be
extended and implemented for any higher number of input digits
by a proper incorporation of dark-bright soliton conversion con-
trol base optical switches.
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1. J. Cong, X. Zhang, and D. Huang, A propose for two-input arbi-
trary Boolean logic gates using single semiconductor optical ampli-
fier by picosecond pulse injection, Opt Exp 17 (2009), 7725–7730.
2. S.H. Kim, J.H. Kim, B.G. Yu, Y.T. Byun, Y.M. Jeon, S.Lee, and
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VC 2011 Wiley Periodicals, Inc.
A HIGH DUTY FACTOR 35-GHz PULSECOMPRESSION WEATHER RADAR ANDRAINFALL OBSERVATION
Hoon Lee and Yong-Hoon Kim
School of Information and Mechatronics, Gwangju Institute ofScience and Technology, 261 Cheomdan-gwagiro, Buk-gu,Gwangju 500�712, Republic of Korea; Corresponding author:[email protected]
Received 29 September 2010
ABSTRACT: A new millimeter wavelength vertical weather radarsystem has been developed. It uses pulse compression technique and has
the characteristics of more than half of duty factor with 5 W solid-statepower amplifier. Nonlinear FM waveforms based on Blackmanharris
function at transmitter are generated for range sidelobe suppression. Wesuccessfully obtained equivalent radar reflectivity and Doppler meanvelocity and these were compared with MRR at moderate rain events for
the system verification. VC 2011 Wiley Periodicals, Inc. Microwave Opt
Technol Lett 53:1544–1547, 2011; View this article online at
wileyonlinelibrary.com. DOI 10.1002/mop.26026
Key words: weather radar; millimeter wave radar; pulse compression;nonlinear waveform
1. INTRODUCTION
Out of many meteorological sensors, radar has a significant role
especially in a short-term prediction and for the warnings of haz-
ardous weather. Current operational weather radars are mostly S-
or C-band, bulky, high power, long range, pulse radars. These
cannot be effective for the network extension in surroundings
with much terrain blockages like the mountainous area. There are
researches to supplement or substitute such long range radar net-
works with short-wavelength distributed networks of small radar
systems via groups such as CASA [1]. Meanwhile, there are
researches to use a pulse compression technique in weather radar
to get a finer range resolution with a lower peak power. For a
given resolution, as opposed to pulse radar, it is estimated to pro-
vide increased sensitivity, possibility of lower measurement error
and higher scan speeds [2]. Although FMCW radars have been
used for certain application, linearity is critical for the range accu-
racy, but for pulse compression modulation is not limited to linear
chirp. We started to base our research on two streams above. We
developed a test-bed and performed initial experiments [3]. In
this article, detailed description of our radar structure is stated
and new experimental results are presented. For nonlinear wave-
form generation in the transmitter Blackman–Harris window
function is selected. We observed moderate rainfall and estimated
equivalent reflectivity and mean velocity. They were compared
with the data by Micro Rain Radar (MRR) which is vertically
pointing 24-GHz FMCW radar [4].
2. SYSTEM DESCRIPTION
A block diagram of the developed Ka-band radar is shown in
Figure 1. This radar system consists of a waveform generator, a
transmitter, two antennas, a receiver, two local oscillators, data
1544 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 53, No. 7, July 2011 DOI 10.1002/mop
acquisition unit, and digital signal processing part. For fully
coherent processing, direct digital synthesizer (DDS), field pro-
grammable gate array (FPGA), data acquisition of digital re-
ceiver and two-phased lock loops for local oscillators (LO) are
synchronized with a common reference clock.
2.1. Waveform GeneratorUsing DDS and fast FPGA control, 38.75–48.75 MHz of nonlinear
waveform were generated using Blackman–Harris window function
for good range sidelobe performance. For 10 MHz of FM bandwidth
and 128-ls pulsewidth, delta frequency, which means regular inter-
val change in frequency value was obtained and saved at FPGA.
Pulse repetition interval were designed as 250-ls considering drop
velocity of rain. Triggering signal which revealed the starting point
of the generated pulse is transferred to digital receiver unit.
2.2. TransmitterBaseband chirp signal was converted to 450 ~ 500 MHz interme-
diate frequency (IF) region, depending on selected channel fre-
quency by 2nd LO using a single sideband mixer. It has the more
than 40 dB of image rejection characteristic. After amplification
and filtering, signal was again converted to 35.5–36 GHz radio
frequency (RF) region, depending on selected band frequency by
1st LO using a double balanced mixer. After RF bandpass filter,
solid-sate high power amplifier (HPA) was used for amplification
up to 5 W. Around 51.2% duty factor is achieved with the use of
HPA. In practical pulse compression weather radar at Ref. 5, only
4% of duty factor is achieved with TWT power device. High duty
factor system can decrease the peak transmitter power, but range
sidelobe effects are lasted up to long ranges.
2.3. AntennasWe used separated antennas for the transmitter and receiver to
detect targets near the ground considering long pulse duration. Pre-
viously developed plano-convex type lens antenna feeing with cor-
rugated circular horn were used [6]. It showed the gain of 36 dBi, 3
dB beamwidth of 2.2� and less than�30 dB of sidelobe level.
2.4. Receiver2.8-dB low noise amplifier is used and total receiver noise figure
is maintained below 4 dB. Using 1st LO, RF signal down-con-
verted to IF but it is directly connected to digital receiver unit
with additional amplifying and filtering.
2.5. Digital Receiver and Signal ProcessingIF signal is down converted by 100-MHz analog digital convert-
ing step using under-sampling (bandpass sampling) technique.
This is for extracting adjacent radar sites’ information in future
network application. Digital processing is divided into two proc-
essing, a signal processing by extracting IQ data via pulse com-
pression and a data processing to extract meteorological parame-
ters, i.e., equivalent radar reflectivity and velocity from IQ data.
These were built-in MATLAB.
3. EXPERIMENTAL SETUP
The developed radar was installed at national institute of mete-
orological research (NIMR) Daekwanryoung site, Gangwon
province, Korea in July of 2010 as shown in Figure 2. It was
covered with thin vinyl for protecting modules during
Figure 1 Block diagram of the Ka-band fully coherent Doppler weather radar
Figure 2 Experimental Set-up at NIMR Daekwanryong site, on July
of 2010. [Color figure can be viewed in the online issue, which is avail-
able at wileyonlinelibrary.com]
DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 53, No. 7, July 2011 1545
measurements. MRR was located at 10 m away, and there are
additional meteorological equipments at that site. MRR data
were acquired as an initial setup of 30 s time resolution, 200-m
range resolution and 30 range gates. Our radar captured 64 num-
bers of pulses every 2 or 5 s and stored to PC. The display reso-
lution was 12 m and effective number of range gate was 1525.
4. EXPERIMENTAL RESULT
Although there are differences between our radar and MRR in
terms of frequency, transmitting power, antenna, modulation, data
processing, etc, the overall patterns of reflectivity profiles are sim-
ilar. Figures 3 (a) and 3(b) shows time-height cross section of ra-
dar reflectivity factor by MRR and our developed radar respec-
tively. For our radar, time and spatial resolutions are better and
sensitivity is enhanced. Estimated reflectivity value is relative low
mainly due to frequency difference. Additional algorithms for
considering attenuation and Mie scattering effect will be necessary
for the next step. Although the isolation between transmitter and
receiver is more than 70 dB, considerable power is still transferred
from transmitter to receiver directly. It affects as a horizontal line
at (b) after processing. Figures 4 (a) and 4(b) shows the estimated
reflectivity and mean Doppler velocity of our radar for the strati-
form type rainfall on July 17, 2010. At 3.6 km, the bright band,
where ice particles changes into water and the reflectivity grows
up rapidly, were observed. Figures 5 (a) and 5(b) shows the verti-
cal profile of radar reflectivity and mean Doppler velocity with
bright band at 01:10 in Figure 4. For comparison with MRR data,
extracted data were again averaged for 30 s in time and 200 m in
space. Although MRR data were processed smoothly, the overall
structure shows quite similar pattern. Our radar has finer resolu-
tion and the detailed structure of rain is clearly shown.
5. CONCLUSIONS
In this study, we have developed the Ka-band weather radar and
observed precipitation events vertically. Using nonlinear wave-
form and pulse compression technique, the radar was imple-
mented with solid-state amplifier as a 51.2% duty factor system.
The observation shows the structure of rainfall successfully with
finer resolution in time and space. Real time signal processing is
Figure 3 Time-height cross section of radar reflectivity factor by (a)
MRR (b) our radar on July 16, 2010. [Color figure can be viewed in the
online issue, which is available at wileyonlinelibrary.com]
Figure 4 Time-height cross section of (a) radar reflectivity and (b)
mean Doppler velocity measured on July 17, 2010. [Color figure can be
viewed in the online issue, which is available at wileyonlinelibrary.com]
Figure 5 Vertical profile of averaged (a) radar reflectivity and (b)
mean Doppler velocity at 01:10 in Figure 4. [Color figure can be viewed
in the online issue, which is available at wileyonlinelibrary.com]
1546 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 53, No. 7, July 2011 DOI 10.1002/mop
being implemented in our group. Furthermore, the compensa-
tions of algorithm will be kept on.
ACKNOWLEDGMENTS
This work was supported in part by the Brain Korea program
(BK21) at Gwangju Institute of Science and Technology, Korea
and millisys, Inc. of Korea.
REFERENCES
1. D. McLaughlin, D. Pepyne, V. Chandrasekar, B. Philips, J. Kurose,
M. Zink, K. Droegemeier, S. Cruz-Pol, F. Junyent, J. Brotzge, D.
Westbrook, N. Bharadwaj, Y. Wang, E. Lyons, K. Hondl, Y. Liu,
E. Knapp, M. Xue, A. Hopf, K. Kloesel, A. Defonzo, P. Kollias,
K. Brewster, R. Contreras, B. Dolan, T. Djaferis, E. Insanic, S.
Frasier, and F. Carr, Short-wavelength technology and the potential
for distributed networks of samll radar systems, Bull Am Meteorol
Soc 90 (2009), 1797–1817.
2. T. Puhakka, V. Chandrasekar, and P. Puhakka, Evaluation of FM
pulse compression for weather radars, AMS 33rd Conference on
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3. H. Lee and Y.H. Kim, Weather radar network with pulse compres-
sion of arbitrary nonlinear waveforms: Ka-band test-bed and initial
observations, Prog Electromagn Res B 25 (2010), 75–92.
4. Available at: http://www.metek.de/produkte.htm.
5. F.O’.Hora and J. Bech, Improving weather radar observation using
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6. H. Lee and Y. H. Kim, A 35 GHz narrow beam lens antenna for
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VC 2011 Wiley Periodicals, Inc.
BANDWIDTH ENHANCEMENT OFA U-SLOT PATCH ANTENNA USINGDUAL-BAND FREQUENCY-SELECTIVESURFACE WITH DOUBLE RECTANGULARRING ELEMENTS
Hsing-Yi Chen and Yu Tao
Department of Communications Engineering, Yuan Ze University,135 Yuan-Tung Road, Nei-Li, Chung-Li, Taoyuan Shian 32003,Taiwan; Corresponding author: [email protected]
Received 29 September 2010
ABSTRACT: A design strategy using a dual-band frequency-selectivesurface (FSS) consisting of double rectangular ring elements to improve
the bandwidth and gain and to optimize the onsets of two operatingfrequencies for a U-slot patch antenna is presented. After implanting the
FSS in the U-slot patch antenna, it was found that the bandwidths havebeen improved from 3.14% to 5.51% and 5.48% to 7.48% at resonantfrequencies 2.45 and 5.8 GHz, respectively. It was also found that the
antenna gain and the onset of operating frequency have been improvedfor Bluetooth and wireless local area network (WLAN) applications. TheU-slot patch antenna implanted with a FSS consisting of double
rectangular ring elements is capable of dual-band operations at 2.45and 5.8 GHz. The radiation patterns are satisfied at these dual bands.VC 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:1547–
1553, 2011; View this article online at wileyonlinelibrary.com.
DOI 10.1002/mop.26066
Key words: frequency-selective surface; U-slot patch antenna;bandwidth; gain; radiation patterns
1. INTRODUCTION
A patch antenna has inherent advantages of small size, low pro-
file, lightweight, cost effect, and its ease of integration with
other circuits. It is very suitable for applications in wireless
communication systems. For today’s wireless communications,
multiband and wide-band patch antennas will become the
requirements for accurately transmitting the voice, data, video,
and multimedia information. However, the most serious problem
of a patch antenna is its narrow bandwidth because a patch
antenna on a dielectric substrate has a very narrow bandwidth due
to surface wave losses. Therefore, how to enhance the bandwidth
and frequency bands of a patch antenna has become an important
issue in the antenna design field. In recent years, to achieve multi-
band and wide-band operation in a patch antenna design, the fre-
quency-selective surface (FSS) is implemented or imbedded in a
patch antenna to carry out the goal. The FSS structure has a phe-
nomenon with high impedance surface that reflects the plane
wave in-phase and suppresses surface wave. Therefore, a patch
antenna with one FSS structure can improve its radiation effi-
ciency, bandwidth, gain, and reduce the side lobe and back lobe
level in its radiation pattern. The FSS has been widely applied in
antennas, filters, reflectors, polarizers, absorbers, propagation,
metamaterials, and artificial magnetic conductors for more than
four decades [1–36]. The FSS is usually constructed with periodic
arrays of metallic patches of arbitrary geometries or slots within
metallic screens. Typical FSS geometries are designed by dipoles,
rings, square loops, fractal shapes, etc. The transmission or reflec-
tion characteristic of a FSS depends on the shape, size, periodic-
ity, and geometrical structure of FSS elements.
In this article, a dual-band FSS consisting of double rectan-
gular ring elements was used to study its impact on the band-
widths and resonant frequencies of a U-slot patch antenna oper-
ating near 2.45 and 5.8 GHz. The frequency bands of 2.4–2.485
and 5.725–5.825 GHz are regulated by IEEE 802.11b/g and
802.11a (upper band) for Bluetooth and WLAN applications,
respectively. In simulations, the characteristics of U-slot patch
antennas were obtained by using the Ansoft high-frequency
structure simulator (HFSS, Ansoft, Pittsburgh, PA). Simulation
results of the return loss, radiation pattern, and gain of this U-
slot patch antenna were validated by measurement data.
2. THE ANTENNA AND FSS
Figure 1 shows a U-slot patch antenna and its dimensions. The
dimensions of the patch antenna are 76 � 52 mm2, and the
thickness of the substrate is 4.4 mm. The dimensions of the rec-
tangular U-slot radiator patch are 30 � 54 mm2. The length and
width of the U-slot are 28.4 and 11.2 mm, respectively. The
width of the slot is 2 mm. In our studies, a coaxial line with a
characteristic impedance of 50 X is used as the feed of the U-
slot patch antenna. The inner conductor of the coaxial line is
attached on the top patch going through the dielectric substrate,
Figure 1 A U-slot patch antenna and its dimensions. [Color figure can be
viewed in the online issue, which is available at wileyonlinelibrary.com]
DOI 10.1002/mop MICROWAVE AND OPTICAL TECHNOLOGY LETTERS / Vol. 53, No. 7, July 2011 1547
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