SAR课程实验报告

SAR Imaging Based On the Range Doppler

Algorithm

Introduction

After the course Radar Imaging, I did a simulation experiment in which I try to use Range Doppler Algorithm (RDA) for SAR Imaging. Here is my report for the experiment.

In my simulation experiment, I got an ideal result of 3 point targets imaging based on the RDA on the condition of high squint.

First of all, I would like to give the parameters used in my simulation.

Then it is the flow chart of the algorithm.

Raw radar data

Result Output Result analysis

1.The echo signal

2 (,)rect exp

exp

c

s t j k

T

j

τ

τπτ

⎛

-⎧⎫

⎪⎪

⎛

=⋅-

⎨⎬

⎝

⎪⎪

⎪⎩⎭

⎝⎭

⎧

⋅-

⎨

⎩

This is the echo data

This is the real part of the echo data

2.Range compression and the SRC

To do range compression we can simply add a matched filter

2

()exp{}r rc r r

j f H f K π=

While the SRC filter is 2

()exp{}r src r src

j f H f K π-=

These two filters can be combined as one filter:

2

()exp{}r m r m

j f H f K π=

Where 1/r

m r src

K K K K =

-

This is the signal after range

compression and SRC.

3. Range Cell Migration Correction (RCMC)

The migration factor (,)a r D f V =

()

H j ω()()

i i s t n t +()()

o o s t n t +()

h t

The phase multiplier 44exp{

}exp{}(,)r c r c

rcmc a r j f R f o G D f V c c

ππ-=⋅

Where c o

is the range of the scene center.

This is the signal after RCMC.

4. Azimuth Compression

After RCMC, a matched filter is applied to focus the data in the azimuth direction.

00

4(,)exp{}a r fa j R D f V f H c

π=

The result is as follow:

Data after azimuth compression.

This is the required result. Conclusion

After doing this simulation, I learned more on SAR imaging. It ’s the practical knowledge. I understood how to achieve the algorithm with IDL instead of just understanding it on the book. But I realize that no matter

the algorithm or the understanding of SAR, on which my study is still primary. I’m looking forward to access more and go deeper in this field.

CODE

;====矩形窗函数==================================

function rect,t

sizearr=size(t)

ff=fltarr(sizearr(1))

index=where(abs(t) le 0.5)

ff(index)=1.

return,ff

end

;;==========雷达参数================

c=double(3.e8) ;光速

lamd=double(0.03) ;波长

fc=double(c/lamd) ;载频

Br=double(1.e8) ;发射信号带宽

Kr=double(1.5e13) ;距离调频率

Tu=double(Br/Kr) ;发射脉冲时宽

fs=double(Br*1.5) ;距离采样率

PRF=double(300.0)

Vr=double(100.0)

Na=1024

Nr=2048

R0=double(2.e4)

cita=double(20.*!pi/180) ;波束斜视角(radian)

ta=(dindgen(Na)-Na/2)/PRF ;慢时间

;=====================目标位置参数======================== xx=0

yy=0

x1=30

y1=0

;=====================雷达位置参数======================== x=vr*ta-R0*sin(cita) ;雷达方位位置

y=R0*cos(cita) ;雷达距离位置

dt=double(sqrt(x^2+y^2))

Rref=dt ;参考目标实时距离

oc=Rref[Na/2] ;场景中心距离

;;================== 回波模拟======================= tr=(dindgen(Nr)-Nr/2)/fs+2*oc/c

record=dcomplexarr(Nr) ;一个脉冲记录

data=dcomplexarr(Na,Nr) ;回波二维数组

for ii=0LL,Na-1LL do begin

record=dcomplexarr(Nr)

Rt=sqrt((x(ii)-xx)^2+(y-yy)^2) ;目标到雷达瞬时距离