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%%??Project:????????????Simulation.m???????????????????????????????????????????%%
%%??Author:?????????????BoBo?Li????????????????????????????????????????????????%%
%%??Date??:?????????????September?19th2004????????????????????????????????????%%
%%??Functionality:??????模擬產生原始數據
%%??備注??:????????????????????????????????????????????????????????????????????%%
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clear?all;?%?清除所有的變量
clc;???????%?清屏
close?all;?%?關閉所有的圖形窗口

cj?=?sqrt（-1）;
pi2?=?2*pi;
c?=?3e8;

%
%%?System?Parameters
RanNum?=?1024;
AziNum?=?1024;
PRF?=?100;%?脈沖重復頻率
Va?=?100;%?方位向速度
R0?=?6e3;%?到場景中心的最短距離
%
%%?fast?time?parameters
Klfm?=?6e12;?%?調頻斜率
Tp?=?6e-6;?%?Pulse?duration?time
BandWidth?=?Tp*Klfm;
SapRate?=?50e6;?%?采樣率
flag1?=?SapRate/BandWidth?%采樣率必須大于帶寬
delta_tr?=?1/?SapRate;?%?采樣間隔

Tr?=?delta_tr*[0:RanNum-1];?%?快時間
X0?=?1000;?%?距離向寬度為2X0
Rmin?=?R0?-?X0;?%?
Tr_start?=?2*Rmin/c;
Tr?=?Tr_start?+?Tr;
Range?=?Tr*c/2;
lambda?=?0.3;
fc?=?c/lambda;
wc?=?pi2*fc;
wcm?=?wc?-?0.5*Tp*Klfm;

%ptr?=?exp（cj*wcm+cj*pi*Klfm*Tr.^2）.*（Tr>0?&?Tr%plot（real（ptr））;

%
%%?slow?time?parameters
Fk?=?-2*Va^2/（lambda*R0）;?%?多普勒調頻斜率
Ts?=?6;?%?合成孔徑時間
DoBandWidth?=?abs（Fk）*Ts;?%?Doppler?BandWidth
flag2?=?PRF/DoBandWidth??%?flag2?>?1
PRI?=?1/PRF;%?脈沖重復間隔
Ta?=?PRI*[-AziNum/2:AziNum/2-1];

Azimuth?=?Va*Ta;?%方位
L?=?0.5*Ts*Va;?%?半孔徑

%Td?=?2*Rt/c;
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%%????????SIMULATION
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%?以下使用的是各目標與場景中心的相對距離

ntargets?=?1;?%?點目標的個數，可以選多個。
TARGETS?=zeros（29）;
DX?=?0.5*c*1/BandWidth;
DY?=?Va*1/DoBandWidth;
CENTER?=?[?R0?0?];
%
%%?點目標的坐標與后向散射系數
TARGETS（:1）?=?[?0???0??].‘;????????????????????????sigma（1）=?1;??
TARGETS（:2）?=?[-50*DX??50*DY].‘;???????????????????sigma（2）=?2;?

TARGETS?=?TARGETS?+?CENTER.‘*ones（19）;

%
%%?Generating?the?raw?data
Sr?=?zeros（AziNumRanNum）;
for?i?=?1:ntargets??
Rt?=?sqrt（TARGETS（1i）.^2+Va^2*（Ta-?TARGETS（2i）/Va）.^2）;?%?隨慢時間變化的斜距
Rt?=?Rt.‘;
Td?=?ones（AziNum1）*Tr?-?2*Rt/c*ones（1RanNum）;
Sr?=?Sr?+?sigma（i）*exp（cj*wcm*Td+cj*0.5*pi2*Klfm*Td.^2）.*（?abs（Td）end;
Sr=Sr.*（ones（AziNum1）*exp（-cj*wc*Tr））;?????%?去載頻


%
%%?visualize?the?raw?data
figure（1）;
%G=abs（Sr）;
G=abs（real（Sr））;
xg=max（max（G））;ng=min（min（G））;cg=255/（xg-ng）;
colormap（gray（256））;
image（RangeAzimuth255-cg*（G-ng））;
title（‘the?raw?data‘）;
xlabel（‘Range??meters‘）;
ylabel（‘Azimuth?meters‘）;

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