matlab

杂波模型

clear all;
close all
azi_num=2000; %雷达回波帧数,一帧表示一个重复周期
fr=1000;
lamda0=0.05;
sigmav=1.0;
sigmaf=2*sigmav/lamda0;
randn('state',sum(100*clock));
d1=randn(1,azi_num);
rand('state',7*sum(100*clock)+3);
d2=randn(1,azi_num);
xi=2*sqrt(-2*log(d1)).*cos(2*pi*d2);
xq=2*sqrt(-2*log(d1)).*cos(2*pi*d2);
coe_num=12; %用傅里叶级数展开法求滤波器系数？？？
for n=0:coe_num; 
coeff(n+1)=2*sigmaf*sqrt(pi)*exp(-4*sigmaf^2*pi^2*n^2/fr^2)/fr;
end
for n=1:2*coe_num+1
if n<=coe_num+1
b(n)=1/2*coeff(coe_num+2-n);
else
b(n)=1/2*coeff(n-coe_num);
end
end
%%%生成高斯谱杂波
xxi=conv(b,xi);
xxq=conv(b,xq);
xxi=xxi(coe_num*2+1:azi_num+coe_num*2);
xxq=xxq(coe_num*2+1:azi_num+coe_num*2);
xisigmac=std(xxi);
ximuc=mean(xxi);
yyi=(xxi-ximuc)/xisigmac;
xqsigmac=std(xxq);
xqmuc=mean(xxq)
yyq=(xxq-xqmuc)/xqsigmac;
sigmac=1.2;
yyi=sigmac*yyi;
yyq=sigmac*yyq;
% j=sqrt(-1);
ydata=yyi+j*yyq;
figure(2),
subplot(2,1,1),plot(real(ydata));
title('瑞利杂波时域波形--实部')
subplot(2,1,2),plot(imag(ydata));
title('瑞利杂波时域波形--虚部')
num=100;
maxdat=max(abs(ydata));
mindat=min(abs(ydata)); 
NN=hist(abs(ydata),num);
xpdf1=num*NN/((sum(NN))*(maxdat-mindat));
xaxis1=mindatmaxdat-mindat)/num:maxdat-(maxdat-mindat)/num;
th_va1=(xaxis1./sigmac^2).*exp(-xaxis1.^2./(2*sigmac^2));
figure(3),
plot(xaxis1,xpdf1);
hold ;plot(xaxis1,th_va1,':r');
title('杂波的幅度分布');
xlabel('杂波的幅度')
ylabel('概率密度')
signal=ydata;
signal=signal-mean(signal);
%%%%用burg法来估计功率谱密度
figure(4),
M=256;
psd_dat=pburg(real(signal),32,M,fr);
psd_dat=psd_dat/(max(psd_dat));
freqx=0:0.5*M;
freqx=freqx*fr/M;
plot(freqx,psd_dat);
title('杂波频谱');
xlabel('频率/Hz')
ylabel('功率谱密度')
%%%作出理想的功率谱曲线
powerf=exp(-freqx.^2/(2*sigmaf.^2));
hold
plot(freqx,powerf,':r');