How to shift the pwelch plot

Hi,

I am using the pwelch function to plot signal power spectrum density. Similar to the function "fftshift", I want the first half of the spectrum swapped with second half to put the zero-frequency value in the middle. But I dont know how to do it on the pwelch. Can any one give me some suggestions?

Thanks.

Answer 1

[bym]

pwelch calculates a one sided spectrum by default, therefore, no shifting is required. You can use the option 'twosided' to get the two sided PSD

Answer 2

[Wayne King]

If you really want DC to be in the middle, you can do this.

Fs = 1e3;
t = 0:1/Fs:1-1/Fs;
x = cos(2*pi*100*t)+randn(size(t));
plot(psd(spectrum.welch,x,'Fs',Fs,'CenterDC',true));