認知無線電的能量檢測

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%生成調制信号

fs=100;

%采樣頻率

fc=40;

%載頻

fo=fs/20;

%碼率

L=300;

%信号樣本

t = (0:L-1)*1/fs;

xn=cos(8*pi*fc*t);         

y = xn + randn(size(t));    

figure(1)

plot(t,y)

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%進行能量檢測

NFFT = 2^nextpow2(L);

Y = fft(y,NFFT)/L;

f = fs/2*linspace(0,1,NFFT/2);

figure(2)

plot(f,2*abs(Y(1:NFFT/2)))