untitled4.m

应用离散傅里叶变换DFT

N=512;
Nfft=1024;
Fs=2*pi;
f1=50;
f2=120;
fs=300;
f1=f1/fs;
f2=f2/fs;
n=0:N-1;
xn=sin(2*pi*f1*n)+sin(2*pi*f2*n)+randn(size(n));
L=input('L=');
window=boxcar(L);
noverlap=L/2;
[pxx2,f]=psd(xn,Nfft,Fs,window,noverlap);
plot(f,10*log(pxx2));grid
axis([0 pi -60 60])
xlabel('Frequency')
ylabel('Power Spectral(db)')
title(['Welch PSD Estimate'])