SYSTEM ARCHITECTURE OF RADAR NETWORK FOR MONITORING OF HAZARDOUD WEATHER

Transcription

1 SYSTEM ARCHITECTURE OF RADAR NETWORK FOR MONITORING OF HAZARDOUD WEATHER HOON LEE Gwangju Institute of Science and Technology &.

2 CONTENTS 1. Backgrounds 2. Pulse Compression 3. Radar Network 4. System Architecture 5. Summary

3 BACKGROUNDS (1) Long range, high power, pulse radars - Max. Detection Range: 200 ~ 300 km - Transmitting Device: Magnetron, Klystron - Transmitting Power: > Hundreds of kw - Range Resolution: 150 ~ 600 m - Frequency: S-band, C-band

4 BACKGROUNDS (2) Earth Curvature - Blind region, resolution degradation R (Km) High Power Device - High price of components - Safety (High Voltage) - Interference

5 BACKGROUNDS (3) Torrential rain, snow More precise observation of important, high population density, drainage areas with compact radar system Effective sensing system? Low altitude observation, higher resolution with advanced technologies?

6 BACKGROUNDS (4) Future system : Integrated observing systems Primary radar network Spaced-based radars Short range, supplementary radars Mobile radars Other government & private sector radars Other observation systems ~ Radar profiler

7 PULSE COMPRESSION (1) 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. Modulation - FM (frequency modulation) : linear (chirp radar) or non-linear - PM (phase modulation)

8 PULSE COMPRESSION (2) Advantages and disadvantages of the pulse compression vs. general pulse radar Advantages lower pulse-power suitable for solid state amplifier higher maximum range good range resolution Disadvantages complex signal processing bad minimum range range (time) sidelobes better jamming immunity difficult reconnaissance It is different from FMCW in MRR FMCW radar ~ dependent on linearity of frequency

9 PULSE COMPRESSION (3) Vaisala, (2007) Device: 8 kw TWT

10 PULSE COMPRESSION (4) TRMM GPM (2013) Item KuPR KaPR Swath Width 245 kilometers (km) 120 kilometers (km) Range Resolution 250 meters (m) 250/500 meters (m) Spatial Resolution 5 km (Nadir) 5 km (Nadir) Beam Width 0.71 degrees 0.71 degrees Transmitter 128 Solid State Amplifiers 128 Solid State Amplifiers Peak Transmit Power Pulse Repetition Freq Watts (W) 140 Watts (W) 4100 to 4400 Hertz 4100 to 4400 Hertz Pulse Width two microseconds pulses two microseconds pulses in matched beams two microseconds pulses in interlaced scans Beam Number (25 in matched beams and 24 in interlaced scans)

11 PULSE COMPRESSION (5) Japan (2007) Low-Power High-Resolution Broad Band Radar.. Tomoaki Mega, etc.

12 PULSE COMPRESSION (6) Range time sidelobe ~ Pulse shaping (Time), Windowing (Freq.) Minimum Detection Range (Mono-static case) Hybrid Waveform Design for Blind Zone Detection of the Pulse Compression Radar (., Patent pending) 1 Magnitude

13 PULSE COMPRESSION (7) Path of long range detection 0 Analog receiver end ADC Down converting Lowpass filter Decimation Matched filtering Part of front samples Reference for long pulse Reference for short pulse Data combining Post data processing Down converting Lowpass filter Decimation Matched filtering Path of short range detection Generation of Chirp signal DDS

14 RADAR NETWORK (1) Dual-Doppler Doppler estimation of horizontal wind vector Pinpoint tracking of target features Bistatic, Multistatic scattering measurements + α scanning radars AVA Project (USA) Map all clouds/precipitation within 5-8 km (inner) domain from ARM site

15 RADAR NETWORK (2) CASA : the Center for Collaborative Adaptive Sensing of the Atmosphere [NetRAD] 3-cm radar network Adaptive sensing Multi-Doppler Analysis for improved detection resolution and wind retrieval.

16 RADAR NETWORK (3) [Off The Grid] (240 km) (30 km) Solar Cell, Wireless networking 4 nodes will be deployed

17 RADAR NETWORK (4) Long-range radars 1) Beam overshoot (earth curvature) 2) Degradation of crossbeam resolution with increasing range Enhancements, + Mitigation of data corruption, filling data voids + Multiple view angles in overlapped regions + Adaptive Sensing It is important to investigate cost-effective ways to achieve a sufficiently dense radar network

18 RADAR NETWORK (5) S-band radar network Sub-network of small radars operating at higher frequencies such as X-band. To cover lower altitude below the radar horizon, mountainous regions, low-level boundaries Polarimetric X-band systems: measure hydrologically and climatologically important light to moderate rainfall more accurately. (Martner et al., 2001) Using differential absorption technique, LOS attenuation measurements may provide additional information on precipitation rates or water vapor content. Appropriate networking high bandwidth, real time data processing, transmission Consideration in minimal interference

19 SYSTEM ARCHITECTURE (1) 10 m resolution LFM Bandwidth: 15 MHz Band I Band II Band III CH1 CH2 CH3 CH4 CH5 CH6 CH7 CH8 CH9 CH10 CH11 CH12 Freq. (MHz)

20 SYSTEM ARCHITECTURE (2)

21 SYSTEM ARCHITECTURE (3) System Structure (., Patent pending)

22 SYSTEM ARCHITECTURE (4) Rx. (LNA) RF BPF 9.3 ~ 9.5 GHz LO1 IF BPF LO2 Digital Receiver In digital part, at down-converting step, wanted channel will be selected by changing frequency. That means we can also use bi-static data only by changing IF freq. Band I Band II Band III Frequency Synthesizer CH1/5/9 CH2/6/10 CH3/7/11 CH4/8/12 Tx. (P.A.) RF BPF IF BPF 9.3 ~ 9.5 GHz Filter Bank By selecting channel DDS (Chirp)

23 SYSTEM ARCHITECTURE (5) 4 separated channels (Measured from IF) 1.2 x 10-4 Spectrum of DDS Raw Data x 10-4 Spectrum of DDS Raw Data D DDS R aw(f) 0.6 D DDS R aw(f) Frequency (MHz) Frequency (MHz) 1.8 x 10-4 Spectrum of DDS Raw Data x 10-4 Spectrum of DDS Raw Data DD DS R aw(f) DD DS R aw(f) Frequency (MHz) Frequency (MHz)

24 SYSTEM ARCHITECTURE (6) Received signal & pulse compression (simulation with RF hardware implementation) y1(t), db time(msec)

25 SUMMARY To improve sensing capability of weather especially for bad conditions such as flash flood, torrential rain and heavy snow, it is adequate to add up short (middle) range, compact radar network to current large, long range radars. For this type of radar system, instead of current high power devices, solid state with pulse compression technique will be a better choice by considering i system safety, compactness, and enhanced resolution. Radar system and network architecture were suggested with an example in X- band type and simulated with really implemented circuits it of RF part.

26 Thank You!!!