为何spectrogram输出有多种颜色的分量

N = 1024;
n01 = randn(1,1024);
n02 = randn(1,512);
n03 = randn(1,512);
sig=anabpsk(N,50,0.25);
sig2=anabpsk(N,50,0.25);
y = awgn(sig,snr);
y2 = awgn(sig2,snr);
sig_contac = [n01 y’ n02 y2’ n03]’;
[S,F,T,P] = spectrogram(sig_contac(900:1100),kaiser(128,18),120,128,1E3,‘yaxis’);
plot(F,S);

因为spectrogram输出STFT短时傅里叶变换频谱是信号的每一段输出一个频谱，你选的信号长多种颜色的分量更多，你选的信号短分量就少甚至可能只有一个分量。

（Matlab 2020a）


data1:
plot(F,S(:,1));

data3:
plot(F,S(:,3));

data10:(说明第10段是检测到非噪声既有用信号了)
plot(F,S(:,10));