Thiết kế bộ lọc FIR code Matlab (MATLAB CODE - design FIR filter)

Dưới đây là 2 ví dụ về bộc lọc FIR (MATLAB Code)

function hd = ideal_lp(wc,M);
% Ideal LowPass filter computation
% --------------------------------
% [hd] = ideal_lp(wc,M)
% hd = ideal impulse response between 0 to M-1
% wc = cutoff frequency in radians
% M = length of the ideal filter
%
alpha = (M-1)/2;
n = [0:1:(M-1)];
m = n - alpha + eps;
hd = sin(wc*m) ./ (pi*m);

function [db,mag,pha,grd,w] = freqz_m(b,a);
% Modified version of freqz subroutine
% ------------------------------------
% [db,mag,pha,grd,w] = freqz_m(b,a);
% db    = Relative magnitude in dB computed over 0 to pi radians
% mag = absolute magnitude computed over 0 to pi radians
% pha  = Phase response in radians over 0 to pi radians
% grd   = Group delay over 0 to pi radians
% w     = 501 frequency samples between 0 to pi radians
% b     = numerator polynomial of H(z) (for FIR: b=h)
% a     = denominator polynomial of H(z) (for FIR: a=[1])
%
[H,w] = freqz(b,a,1000,'whole');
H = (H(1:1:501))'; w = (w(1:1:501))';
mag = abs(H);
db = 20*log10((mag+eps)/max(mag));
pha = angle(H);
grd = grpdelay(b,a,w);