freqs_m.m

Digital signal processing using Matlab一書之範例程式

function [db,mag,pha,w] = freqs_m(b,a,wmax);
% Computation of s-domain frequency response: Modified version
% ------------------------------------------------------------
% [db,mag,pha,w] = freqs_m(b,a,wmax);
%   db = Relative magnitude in db over [0 to wmax]
%  mag = Absolute magnitude over [0 to wmax]
%  pha = Phase response in radians over [0 to wmax]
%    w = array of 500 frequency samples between [0 to wmax]
%    b = Numerator polynomial coefficents of Ha(s)
%    a = Denominator polynomial coefficents of Ha(s)
% wmax = Maximum frequency in rad/sec over which response is desired
%
w = [0:1:500]*wmax/500;
H = freqs(b,a,w);
mag = abs(H);
db = 20*log10((mag+eps)/max(mag));
pha = angle(H);