认知无线电 matlab检测方针 能量检测

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%生成bpsk调制信号 fs=100; %采样频率 fc=40; %载频 fo=fs/20; %码率 a=2*fo; %循环周期 T=40; %信号样本 x=rand(40,1); y=round(x); a1=y*2-1; z=ones(200,1); for i=1:40 for j=1:5 an(5*i-5+j)=z(5*i-5+j)*a1(i); end end t=1/fs:1/fs:2; xn=an.*cos(4*pi*fc*t); %生成bpsk调制信号,第一用户使用情况下 figure(1) plot(t,xn); axis([0 2 -1.5 1.5]); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%进行周期图检测 window=kaiser(length(xn),0.5); %矩形窗 nfft=512; %512fft [Pxx,f]=periodogram(xn,window,nfft,fs); %周期图检测 figure(2) plot(f,-10*log10(Pxx)); window=kaiser(length(xn),0.5); nfft=1024; %%%%%%%%%%%%%%%%%%%%%%%%%%%%1024fft [Pxx,f]=periodogram(xn,window,nfft,fs); %周期图检测 figure(3) plot(f,10*log10(Pxx)); %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%对不同类型窗函数进行检测兴性能分析 window1=boxcar(length(xn)); %矩形窗 window2=hamming(length(xn)); %海明窗 window3=blackman(length(xn)); %blackman窗 [Pxx1,f]=periodogram(xn,window1,nfft,fs); [Pxx2,f]=periodogram(xn,window2,nfft,fs); [Pxx3,f]=periodogram(xn,window3,nfft,fs); figure(4) subplot(221) plot(f,-10*log10(Pxx)); subplot(222) plot(f,-10*log10(Pxx1)); subplot(223) plot(f,-10*log10(Pxx2)); subplot(224) plot(f,-10*log10(Pxx3));