hr_type1.m

Digital Signal Processing Using MATLAB V.4随书代码

function [Hr,w,a,L] = Hr_Type1(h);

% Computes Amplitude response Hr(w) of a Type-1 LP FIR filter

% -----------------------------------------------------------

% [Hr,w,a,L] = Hr_Type1(h)

% Hr = Amplitude Response

%  w = 500 frequencies between [0 pi] over which Hr is computed

%  a = Type-1 LP filter coefficients

%  L = Order of Hr

%  h = Type-1 LP filter impulse response

%

 M = length(h);

 L = (M-1)/2;

 a = [h(L+1) 2*h(L:-1:1)]; % 1x(L+1) row vector

 n = [0:1:L];              % (L+1)x1 column vector

 w = [0:1:500]'*pi/500;

Hr = cos(w*n)*a';