function [Hr,w,d,L] = Hr_Type4(h);
% Computes Amplitude response of Type-4 LP FIR filter
% ---------------------------------------------------
% [Hr,w,d,L] = Hr_Type4(h)
% Hr = Amplitude Response
%  w = frequencies between [0 pi] over which Hr is computed
%  d = Type-4 LP filter coefficients
%  L = Order of d
%  h = Type-4 LP impulse response
% 
 M = length(h);
 L = M/2;
 d = 2*[h(L:-1:1)];
 n = [1:1:L]; n = n-0.5;
 w = [0:1:500]'*pi/500;
Hr = sin(w*n)*d';