与那国における海洋レーダ・バイスタティック観測

観測期間： 2012年6月11日～6月14日

川村 誠治, 杉谷 茂夫, 岩井 宏徳, 雨谷 純, 花土 弘

Ocean radar bistatic observation in Yonaguni-island

Seiji Kawamura, Shigeo Sugitani, Hironori Iwai, Jun Amagai, and Hiroshi Hanado

情報通信研究機構

National Institute of Information and Communications Technology

Observation： June 11 - 14, 2012

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.

Bistatic Experiments in Yonaguni Island

120Km 120Km

(closed in 2010)Yonaguni-island Ishigaki-island

Red：TORI routine obs.Center frequency：4.58 MHz

Light blue：TORI test obs.（Sept. 2011）

Center frequency：4.58 MHzBlue：NICT ocean radar

Bistatic Receiving Experiments in Yonaguni IslandExperiments： September 20 – 22, 2011

ch1 ch2 ch3 ch4

Bistatic Receiving Systemin Yonaguni Island

AMP＆Filter

USRP2

Divider of GPS signals

GPS receiver

GPS antenna

10 MHz

1 PPS

LANUSRP2

Signal generator

(for phase calibration)

Screen of spectrum analyzer at Yonaguni island(span: 4.25 – 4.75 MHz)

4.388 MHz 4.58 MHz

送 受 送 受 送 受 送 受 送 受 送 受 送 受 送 受 送 受 送 受 送 受

Frequency

Time

Sw

eep

band

wid

th: B

Sweep time: T

2R/c

Δf

Principle of Ocean Radar (FMICW Radar)

R = ―― Δfc T

2BRange：

4.388 MHz 4.58 MHz

One sweep: 514 pulses for 1 sClear and simple sweep is assumed to be a signal from one ocean radar.

One sweep: 514 pulses for 1 sSignals from some radars are seemed to be mixed.

Sampled Data with USRP2

Transmitted wave（Direct wave） Received signal

Transmitted wave（Direct wave） Received signal

Unknown signal TORI Ocean Radar

Reproduction of Transmitted wave－ using received direct wave ー

I component of received signal

Q component of received signal

Phase

Reproduction of Transmitted wave－ using received direct wave ー

I component of received signal

Q component of received signal

Phase

13:41:47 JST 14:17:50 JST13:59:01 JST

Examples of Retrieved Spectra (4.388 MHz)

Time series of received signal for 256 sec.

Spectra

September 21, 2011

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.

Red：TORI routine obs.Center frequency：4.58 MHz

Light blue：TORI test obs.（Sept. 2011）

Center frequency：4.58 MHz

Blue：NICT ocean radar

Bistatic Receiving Experiments in Yonaguni IslandExperiments： June 11 – 14, 2012

ch5 ch6 ch7 ch8

Bistatic Receiving System in Yonaguni Island

USRP-N210

GPS receiver

GPS antenna

10 MHz

1 PPSLAN

Signal generator

(for phase calibration)

ch1 ch2 ch3 ch4

GPS antenna

1

2

3

4

6

5

7

8PC

USRP-N210

AMP＆FilterDivider of GPS signals

Photos of receiving system

AMP＆Filter・Divider of GPS signals

USRP-N210 (8ch)

GPS receiver

Signal generator

PPS divider

Received signals with each antennaPhase differences between each channels are calibrated.

1945.6 μs

Position of each site

Position of each site

Area of “Bistatic angles are less than 45 degrees”

Position of each site

Direction to each siteSDGO

HOPE

LUYE

SHIA

Received signals from each radar siteReceiving beams are composed to the direction of each radar site.

SDGO HOPE LUYE SHIA

Signal

Spectra

Example of data analysisSpectrum 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)

2012/6/14 06:05 UT （15:05 JST）

Results － Bistatic observation ―

SHIA

LUYEHOPE

SDGO

Northward beam from Yonaguni

2012/6/14 06:05 UT （15:05 JST）

Results － Bistatic observation ―

SDGO HOPE

LUYE SHIA

Rang

e fr

om Y

onag

uni

- 0.156 m/s - 0.242 m/s

- 0.314 m/s - 0.243 m/s

Northward beam from Yonaguni

Google Earth

SDGO

HOPE

LUYESHIA

2012/6/14 06:05 UT （15:05 JST）

0.156 m/s

0.242 m/s

0.314 m/s

0.243 m/s

2D current Estimation

50 km

Yonaguni island

2012/6/14 06:00 UT （15:00 JST）

Monostatic observaion from Yonaguni

- 0.373 m/s

Northward beam

Google Earth

SDGO

HOPE

LUYESHIA

2012/6/14 06:05 UT （15:05 JST）

0.373 m/s

0.156 m/s

0.242 m/s

0.314 m/s

0.243 m/s

0.412 m/s(334.9 °NCW)

2D current Estimation

50 km

Yonaguni island

SummaryBistatic 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.