pcmtitest.m

通过visual DSP

close all; 
clear all;
%===================================================================================%
%                                    雷达参数                                        %
%===================================================================================%
C=3.0e8;  %光速(m/s)
RF=3.140e9;  %雷达射频
Lambda=C/RF;%雷达工作波长
PulseNumber=2;   %回波脉冲数 
BandWidth=2.0e6;  %发射信号带宽
TimeWidth=42.0e-6; %发射信号时宽
PRT=230e-6;   % 雷达发射脉冲重复周期(s)
PRF=1/PRT
Fs=20e6;  %采样频率
%F0=15e6;
F0=0;
NoisePower=-26;%(dB);
%---------------------------------------------------------------%
SampleNumber=fix(Fs*PRT);%计算一个脉冲周期的采样点数；
TotalNumber=SampleNumber*PulseNumber;%总的采样点数；
BlindNumbe=fix(Fs*TimeWidth);%计算一个脉冲周期的盲区-遮挡样点数；
%===================================================================================%
%                                    目标参数                                       %
%===================================================================================%
TargetNumber=3;%目标个数
SigPower(1:TargetNumber)=[1 .5 .3];%目标功率,无量纲
TargetDistance(1:TargetNumber)=[7000 14000 23000];%目标距离,单位m
DelayNumber(1:TargetNumber)=fix(Fs*2*TargetDistance(1:TargetNumber)/C);
TargetVelocity(1:TargetNumber)=[0 30 100];%目标径向速度 单位m/s
TargetFd(1:TargetNumber)=2*TargetVelocity(1:TargetNumber)/Lambda  %计算目标多卜勒
%====================================================================================%
%                                   产生线性调频信号                                     %
%====================================================================================%
number=fix(Fs*TimeWidth);
if rem(number,2)~=0
   number=number+1;
end   
for i=-fix(number/2):fix(number/2)-1
   Chirp(i+fix(number/2)+1)=exp(j*(2*pi*F0*i/Fs+pi*(BandWidth/TimeWidth)*(i/Fs)^2));
end
figure(100)
plot(abs(fftshift(Chirp)));
coeff=conj(Chirp);
coeff=fliplr(coeff);
coeff=real(coeff);
%-------------------------产生目标回波串------------------------%
SignalAdd=zeros(1,TotalNumber);%所有脉冲的信号
for k=1:TargetNumber% 依次产生各个目标
   SignalTemp=zeros(1,SampleNumber);% 一个脉冲
   SignalTemp(DelayNumber(k)+1:DelayNumber(k)+number)=sqrt(SigPower(k))*Chirp;%一个脉冲的某个目标
   Signal=zeros(1,TotalNumber);
   for i=1:PulseNumber
      Signal((i-1)*SampleNumber+1:i*SampleNumber)=SignalTemp;
   end
   FreqMove=exp(j*2*pi*TargetFd(k)*(0:TotalNumber-1)/Fs);
   Signal=Signal.*FreqMove;
   SignalAdd=SignalAdd+Signal;
end
SignalAll=SignalAdd;
 figure(1);
  plot(real(SignalAll));title('目标信号');
  %subplot(2,1,2);plot(imag(SignalAll));title('目标信号的虚部');
 grid on;zoom on;

%====================================================================================%
%                                   产生系统噪声信号                                  %
%====================================================================================%
SystemNoise=normrnd(0,10^(NoisePower/10),1,TotalNumber)+j*normrnd(0,10^(NoisePower/10),1,TotalNumber);
%====================================================================================%
%                                   总的回波信号                                     %
%====================================================================================%
Echo=SignalAll+SystemNoise;% +SeaClutter+TerraClutter;
for i=1:PulseNumber   %在接收机闭锁期,接收的回波为0
      Echo((i-1)*SampleNumber+1:(i-1)*SampleNumber+number)=0;
end
Echo=real(Echo);

 figure(2);
 plot(Echo);title('总回波信号,闭锁期为0');
 %subplot(2,1,2);plot(imag(Echo));title('总回波信号的虚部,闭锁期为0');
% 
%================================时域脉压=================================%
pc_time0=conv(Echo,coeff);
figure(3);plot(20*log10(abs(pc_time0)));title('时域脉压结果的幅度,有暂态点');
pc_time1=pc_time0(number:TotalNumber+number-1);%去掉暂态点 number-1个
%================================频域脉压=================================%
%Echo_fft=fft(Echo,TotalNumber+number-1);
% coeff_fft=fft(coeff,TotalNumber+number-1);
Echo_fft=fft(Echo,TotalNumber+number-1);%理应进行TotalNumber+number-1点FFT,但为了提高运算速度,进行了1024点的FFT
% figure(13);plot(real(Echo_fft));
% figure(14);plot(imag(Echo_fft));
coeff_fft=fft(coeff,TotalNumber+number-1);
pc_fft=Echo_fft.*coeff_fft;
% figure(11);plot(real(pc_fft));
% figure(12);plot(imag(pc_fft));
pc_freq0=ifft(pc_fft);
figure(4);plot(abs(real(pc_freq0)));title('实部脉压结果');
%figure(5);plot(imag(pc_freq0));title('iamg pulse solution');
figure(6);plot(abs(pc_freq0));title('频域脉压结果的幅度,有暂态点和后填充点,');
frequ0=abs(pc_freq0);
save module.dat frequ0  -ascii -double 
plot(abs(pc_time0(1:TotalNumber+number-1)-pc_freq0(1:TotalNumber+number-1)),'r');hold on;
pc_freq1=pc_freq0(number:TotalNumber+number-1);%去掉暂态点 number-1个,后填充点若干(1024-number+1-TotalNumber=21个)
% save pc_freq1.dat pc_freq1 -ascii -double 
%================MTI,对消静止目标和低速目标---相当于杂波=================================%
mti=pc_time1(SampleNumber+1:2*SampleNumber)-pc_time1(1:SampleNumber);
remti=real(mti);
immti=imag(mti);
figure(8);plot(real(mti));title('MTI real 结果');
figure(9);plot(imag(mti));title('MTI imag 结果');
mti_module=abs(mti);
% save remti.dat remti -ascii -double 
% save immti.dat immti -ascii -double 
% save mtimodule.dat mti_module -ascii -double
figure(10);plot(abs(mti));title('MTI 结果');