p200-1.m

在傅立叶变换时加入适当的时间窗

clear
k=4;T=5;
fc=k*T;
fs=4*fc;
Ts=1/fs;
N=T/Ts;
x=zeros(1,N);
nfft=min(256,length(x));
window=hanning(22);
noverlap=length(window)/2;
t=0:N-1;
x=exp(j*k*pi*(t*Ts).^2);
specgram(x,nfft,fs,window,noverlap);