Ocean radar bistatic observation in Yonaguni-island

Transcription

1 Ocean radar bistatic observation in Yonaguni-island 与那国における海洋レーダ バイスタティック観測 Observation: June 11-14, 2012 観測期間 : 2012 年 6 月 11 日 ~6 月 14 日 Seiji Kawamura, Shigeo Sugitani, Hironori Iwai, Jun Amagai, and Hiroshi Hanado 川村誠治, 杉谷茂夫, 岩井宏徳, 雨谷純, 花土弘 National Institute of Information and Communications Technology 情報通信研究機構

2 Contents Bistatic receiving experiments with software radio receivers in Yonaguni island. Targets are Taiwan ocean radars. Last year, we retrieved Doppler spectra using unknown radio waves. An example of passive radar. This year, we received radio waves from 4 Taiwan ocean radars, and estimate surface current with the bistatic method.

3 Bistatic Experiments in Yonaguni Island 120Km Yonaguni-island 120Km Ishigaki-island (closed in 2010)

4 Bistatic Receiving Experiments in Yonaguni Island Experiments: September 20 22, 2011 Red:TORI routine obs. Center frequency:4.58 MHz Blue:NICT ocean radar Light blue:tori test obs. (Sept. 2011) Center frequency:4.58 MHz

5 Bistatic Receiving System in Yonaguni Island ch1 ch2 ch3 ch4 GPS antenna GPS receiver 10 MHz AMP& Filter USRP2 Signal generator (for phase calibration) Divider of GPS signals 1 PPS USRP2 LAN

6 Screen of spectrum analyzer at Yonaguni island (span: MHz) MHz 4.58 MHz

7 Principle of Ocean Radar (FMICW Radar) Frequency Sweep band width: B 2R/c Δf 送受送受送受送受送受送受送受送受送受送受送受 Time Sweep time: T Range: c T R = Δf 2B

8 Sampled Data with USRP2 Unknown signal TORI Ocean Radar MHz 4.58 MHz Transmitted wave (Direct wave) Received signal Transmitted wave (Direct wave) Received signal One sweep: 514 pulses for 1 s Clear and simple sweep is assumed to be a signal from one ocean radar. One sweep: 514 pulses for 1 s Signals from some radars are seemed to be mixed.

9 Reproduction of Transmitted wave - using received direct wave ー I component of received signal Q component of received signal Phase

10 Reproduction of Transmitted wave - using received direct wave ー I component of received signal Q component of received signal Phase

11 Examples of Retrieved Spectra (4.388 MHz) September 21, 2011 Time series of received signal for 256 sec. 13:41:47 JST 13:59:01 JST 14:17:50 JST Spectra

12 Summary of experiments in last year Unknown radio waves are analyzed. We do NOT know the position, sweep frequency, delay time, and so on. We retrieved Doppler spectra by reproducing transmitted waves from direct received signals. An example of Passive Radar. Accuracy of estimated frequency (sweep band) of transmitted wave is important. This year, we try to analyze signals from known four Taiwan ocean radars, whose frequency is 4.58 MHz.

13 Bistatic Receiving Experiments in Yonaguni Island Experiments: June 11 14, 2012 Red:TORI routine obs. Center frequency:4.58 MHz Blue:NICT ocean radar Light blue:tori test obs. (Sept. 2011) Center frequency:4.58 MHz

14 Bistatic Receiving System in Yonaguni Island ch1 ch2 ch3 ch4 ch5 ch6 ch7 ch8 GPS antenna Signal generator GPS receiver 10 MHz (for phase calibration) USRP-N210 1 PPS AMP&Filter Divider of GPS signals USRP-N210 LAN GPS antenna PC

15 Photos of receiving system PPS divider GPS receiver AMP&Filter Divider of GPS signals USRP-N210 (8ch) Signal generator

16 Received signals with each antenna Phase differences between each channels are calibrated μs

17 Position of each site

18 Position of each site

19 Position of each site Area of Bistatic angles are less than 45 degrees

20 SDGO Direction to each site HOPE LUYE SHIA

21 Received signals from each radar site Receiving beams are composed to the direction of each radar site. SDGO HOPE LUYE SHIA Signal Spectra

22 Example of data analysis Spectrum of received signal Spectrum of re-producted transmitted wave Spectrum of beat signal Spectrum of beat signal after low pass filtering Time series of beat signal Ranged signal (FFT of beat signal time series)

23 Results - Bistatic observation 2012/6/14 06:05 UT (15:05 JST) Northward beam from Yonaguni SDGO HOPE LUYE SHIA

24 Results - Bistatic observation 2012/6/14 06:05 UT (15:05 JST) Northward beam from Yonaguni Range from Yonaguni SDGO HOPE m/s m/s LUYE SHIA m/s m/s

25 2D current Estimation 2012/6/14 06:05 UT (15:05 JST) m/s m/s m/s SDGO m/s 50 km HOPE LUYE SHIA Yonaguni island Google Earth

26 Monostatic observaion from Yonaguni 2012/6/14 06:00 UT (15:00 JST) Northward beam m/s

27 2D current Estimation 2012/6/14 06:05 UT (15:05 JST) m/s (334.9 NCW) m/s m/s m/s m/s SDGO m/s 50 km HOPE LUYE SHIA Yonaguni island Google Earth

28 Summary Bistatic observation are conducted during June 11 to 14, 2012 in Yonaguni island. Receiving system is (a little bit) upgraded from last year. GPS time handling, number of channels is 4 to 8, and so on. Signals from 4 Taiwan ocean radar, whose frequency is 4.58 MHz, are analyzed. Using known information for each site (position, sweep frequency, delay time, and so on), we retrieved signal from each radar at the same time. From Doppler spectra from each site and from Yonaguni radar, 2D surface current is estimated. In future, we want to estimate 2D surface current for wider area using 8ch DBF. validate 2D surface current.