MATLAB: Extract values from Nyquist for negative frequencies

Question

Hi,

is there a way of extracting values (Real part & Imaginary part) from the nyquist plot for the negative frequencies? At the moment I am using the following code:

[re,im,w_h] = nyquist(h);
Re = squeeze(re);
Im = squeeze(im);

This code only gives me the Real- and Imaginary part values for positive frequencies. "w_h" is always postivie even though nyquist also has negative frequencies.

Thanks very much for your help!

Answer 1

The Nyquist plot is symmetric, so the compex cojugate of the output would correspond to the negative frequencies.

[re_pos,im_pos,w_h] = nyquist(h);
re_neg =  re_pos;
im_neg = -im_pos;