clear all; close all;
azi_num = 2000;
fr = 1000;
lamda0 = 0.05;
sigmav = 1.0;
sigmaf = 2*sigmav/lamda0;

randRes=spRand(0,1,azi_num);%生成兩組互相獨立的高斯隨機數
%求濾波器系數
BT = .3; 
OF = 6;   
NT = 2;  
b = gaussfir(BT,NT,OF);
%生成高斯譜雜波
xxi = conv(b,randRes(1,:));
%去掉暫態響應
yyi=disZ(xxi,NT,OF,azi_num);

muc=10;     %中位值
sigmac=0.6; %形狀參數

yyi=sigmac*yyi+log(muc);
ydata=exp(yyi);
figure,plot(ydata);

%仿真結果的概率密度
pdfRes=pdfPlot(abs(ydata),100);
%概率密度函數理論值
th_val=lognpdf(pdfRes(1,:),log(muc),sigmac);
figure(2)
plot(pdfRes(1,:),pdfRes(2,:),pdfRes(1,:),th_val,'r:');
title('雜波幅度分布');xlabel('幅度');ylabel('概率密度');

%求功率譜密度
signal = ydata;
signal = signal-mean(signal);%去直充分量
[psd_dat,freqx]=pburg(real(signal),16,128,fr);  %%%用Burg法估計功率譜密度
psd_dat=psd_dat/(max(psd_dat));      %歸一化處理
powerf=exp(-freqx.^2/(2*sigmaf.^2)); %理想高斯譜曲線
figure(3)
plot(freqx,psd_dat,freqx,powerf,':r');
title('雜波頻譜');xlabel('頻率(Hz)');ylabel('功率譜密度');