The 10th Weather Radar Workshop
Design and Initial Test
of Ka-band Pulse Compression Radar
for Vertical Observation of Weather Signals
2009. 12. 18
Hoon Lee*, Jin-Mi Jeong, Yong-Hoon Kim
millisys, Inc. &
Gwangju Institute of Science and Technology
http://www.millisys.com
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CONTENTS
The 10th Weather Radar Workshop
v BACKGROUNDS
v REQUIREMENTS
v SYSTEM DESIGN
v SYSTEM IMPLEMENTATION
v INITIAL GROUND TARGETS TEST
v SUMMARY
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BACKGROUNDS (1)
The 10th Weather Radar Workshop
v MMW Radars in Atmospheric Research
[ Millimeter-Wavelength Radars: P. Kollias etc.]
§ Supplement the dynamic range of cm-wavelength radars
§ Dual-wavelength measurements and non-Rayleigh scattering
§ Less susceptible than cm-wavelength radars to Bragg scattering
§ Less susceptible to ground clutter
§ Deployable on mobile systems
§ Applications of MMW cloud radar in atmospheric research
§ Cloud layer statistics
§ Turbulence, microphysics, and process studies
§ in clouds and precipitation
l (중대형 레이더 보완 + 새로운 정보의 제공 가능)
[Sensitivity]
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Sensitivity of radars (95 GHz: low Tx. power, high attenuation)
[Attenuation]
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BACKGROUNDS (2)
The 10th Weather Radar Workshop
v Vertical Weather Radar System
MRR-2 (METEK)
VertiX (McGill)
Type
Band
Frequency
Bandwidth
FMCW
K
24.1 GHz
1.5 ~ 15 MHz
Pulse Doppler
X
9.4 GHz
1~20 MHz (Pulsewidth)
Output parameter
Radar Reflectivity (dBZ)
Vertical Doppler velocity (m/s)
Average power spectra (dBη)
=> calculated values like DSD
Radar Reflectivity (dBZ)
Vertical Doppler velocity (m/s)
Average power spectra
Ant. Type
Ant. Size
Ant. Gain
Ant. Beamwidth
Pointing angle
Parabola, offset feed
0.6 m diameter
> 40 dBi
< 2°
Vertical
Parabola
1.2 m diameter
39 dB or more
1.8°
Vertical
Power Device
Power
Gunn Oscillator
50 mW
Magnetron
23 KW, peak
Pulse width
Space resolution
10 m ~ 1 Km
50/250/500/1000 nsec
7.5/37.5/75/150 m
Number of gates
Distance
30
300 m (min) ~ 30 Km (Max.)
6 Km 이상은 only test
12 Km (useful)
Sample time
PRF
10 sec ~ 1 hour
_
2 sec
1300 Hz
Size
Weight
Rx. DR
Rx. Type
GIST
12 Kg
2.4 * 1 * 1 m
300 Kg
75 dB
Superheterodyne
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BACKGROUNDS (3)
The 10th Weather Radar Workshop
v Pulse Compression Radar
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The pulse compression ?
~ the process of transforming a signal with wide time duration into a pulse with much narrower duration to get high range resolution.
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Modulation
- FM (frequency modulation) : linear (chirp radar) or non-linear
- PM (phase modulation)
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Advantages and disadvantages of the pulse compression vs. general pulse radar
Advantages
Disadvantages
lower pulse-power
suitable for solid state amplifier
complex signal processing
higher maximum range
bad minimum range
good range resolution
range (time) sidelobes
[Applications in Weather Radar]
Vaisala 사
TRMM → GPM (2013)
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The 10th Weather Radar Workshop
REQUIREMENTS
v Initial Requirements
Requirements
Initial targets
Object target
(Sensitivity)
(Cloud) -30 dBZ @ 10 Km
Range
min. ~ Max. : (0~ 15 Km)
(Resolution : 15 m~)
-10 MHz bandwidth
Velocity
normal: -10 ~ +10 m/sec
(Max. : -20 ~ +20 m/sec)
(Resolution : 0.1 m/sec)
- (모든 물체는 일정 속도에 이르면 떨어지는 물체에 작용하는 중력
과 공기저항이 같아져 더 이상 낙하 속도가 빨라지지 않고 일정한
속도가 되는 때가 온다는 것.) 장마철 폭우의 빗방울 직경이 약 3㎜
라면 종단속도는 초당 8~9ｍ
Antenna
Beam width : (2.2°)
Z, V, W
- Ka-band의 장점을 살려야함.
- Minimum Detectable Signal
(중간층 강우 감쇄가 없는 것으로 가정)
- 0.3 m diameter (기 개발 Lens Ant. 이용)
(+ LDR ?)
- Attenuation correction algorithm 개발 시 적용
- FFT 방법으로 추출 (PPP 방법도 고려)
- Dual Pol. 적용 경우, ice particle의 wind (shear)에 의한 영향
Time Resolution
(~ 수 초)
- 데이터 갱신 속도
기타
크기, 무게 등
Parameters
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Reference
- 가능한 최소화
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SYSTEM DESIGN (1)
The 10th Weather Radar Workshop
v Radar Equation (Pulse compression 고려, Bi-static case)
× Вτ / Lextra
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SYSTEM DESIGN (2)
The 10th Weather Radar Workshop
v System Configuration
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Transmitter
Waveform Generation
Receiver
Data Acquisition,
Signal Processing
Data Processing,
System Control, Display
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IMPLEMENTATION (1)
The 10th Weather Radar Workshop
v DDS Waveform Generation
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FPGA : Altera cyclone EP1C69240C8
n
Referance clock : 10 MHz
n
1 clk 1 data transfer
n
LFM, NLFM and pulse shaping
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DDS 칩 AD9854
n
Ref clock : 200MHz
n
128 usec long pulse : 160 step. control
n
Pulse repetition Interval : 250 usec
Data 8bit
FPGA
Address 6bit
DDS
AD9854
Control 6bit
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IMPLEMENTATION (2)
The 10th Weather Radar Workshop
v RF/IF Module
Tx_IF
Tx_RF
Rx_RF
Rx_IF
CLK Divider
PLL/Synthesizer
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IMPLEMENTATION (3)
The 10th Weather Radar Workshop
v Lens Antenna
Ant. Measurements
Horizontal Beam Pattern
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IMPLEMENTATION (4)
The 10th Weather Radar Workshop
v Data Acquisition & Signal Processing
ChA
ADC
FPGA
(Algo)
ChB
Clock
FPGA
(Comm)
USB
ADC
Triger
I/Q Generation
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IMPLEMENTATION (5)
The 10th Weather Radar Workshop
v Data Processing – Doppler Processing (FFT)
Range-Doppler Analysis
for ideal fixed targets
Signal/Data Processing
using Matlab
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IMPLEMENTATION (6)
The 10th Weather Radar Workshop
v Ant. / WG RF Components Assembly
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INITIAL TEST (1)
The 10th Weather Radar Workshop
v Ground Test Setup with Standard Horn Ant.
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The 10th Weather Radar Workshop
INITIAL TEST (2)
v Ground Test with Standard Horn Ant.
Spectrum of Reference
30
5000
H1(f)
Amp.(ADC-Integer)
H channel(1 PRI
0
20
10
-5000
0
1
2
3
4
Sample Number
0
5
2
Relative Power
|X1(f)|
40
20
0
0
0
1
0
5
10
Frequency (MHz)
5
Target
x 10 Reflection @ 1st Pulse
0
GIST
-20
-40
-60
-80
0
0.5
1
1.5
2
Distance(km)
Target Reflection @ 1st Pulse
0
-20
-40
-60
-80
0
0.5
1
1.5
Distance(km)
2
500
Time (usec)
1000
Target Reflection @ 1st Pulse
Relative Power(dB)
0
Relative Power(dB)
Relative Power(dB)
Relative Power(dB)
Target Reflection @ 1st Pulse
Main (front) Target is Oryong-hall which is from 150 m.
Several same tests showed similar results.
5
10
Frequency (MHz)
4
x 10
Spectrum of Received Data
0
-20
-40
-60
-80
0
0.5
1
1.5
2
Distance(km)
Target Reflection @ 1st Pulse
0
-20
-40
-60
-80
0
50
100
Distance(km)
150
millisys, Inc
The 10th Weather Radar Workshop
INITIAL TEST (3)
v Ground Test with Standard Horn Ant.
Spectrum of Reference
30
5000
H1(f)
Amp.(ADC-Integer)
H channel(1 PRI
0
20
10
-5000
0
1
2
3
4
Sample Number
0
5
4
Relative Power
|X1(f)|
100
50
0
0
0
5
10
Frequency (MHz)
4
x 10
Spectrum of Received Data
2
0
5
10
Frequency (MHz)
5
Target
x 10 Reflection @ 1st Pulse
0
500
Time (usec)
GIST
-40
-60
-80
0
0.5
1
1.5
2
Distance(km)
Target Reflection @ 1st Pulse
0
-20
-40
-60
-80
0
0.5
1
1.5
Distance(km)
2
Relative Power(dB)
-20
Target Reflection @ 1st Pulse
Relative Power(dB)
Relative Power(dB)
Main (front) Targets are APTs which are from 500 m.
Several tests showed similar results.
Relative Power(dB)
Target Reflection @ 1st Pulse
0
1000
0
-20
-40
-60
-80
0
0.5
1
1.5
2
Distance(km)
Target Reflection @ 1st Pulse
0
-20
-40
-60
-80
0
50
100
Distance(km)
150
millisys, Inc
The 10th Weather Radar Workshop
SUMMARY & FUTURE PLAN
v
Ka-band vertical radar will be very useful in meteorological researches.
(because of its compactness, enhanced sensitivity)
v
Instead of current high power devices such as magnetron, solid state with pulse compression
technique is better considering system safety, compactness, and enhanced resolution.
v
A vertical prototype system has been designed step by step from initial system requirements.
v
Sub-system and Modules have been designed, implemented and tested.
v
Signal Processing and Data Processing algorithms are being developed and tested with high speed
Data acquisition system and MATLAB.
(RF Integration & FPGA + DSP hardware development will be a next stage)
v
We are now preparing meteorological target observation from this winter.
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