dfiropt.m

trabajos en matlab para verificar son muy buenos

function hwn = dfiropt(ty,n,a,sf,fp,fs)
% Impulse response for optimal design
% This will be used to find and plot the spectrum (see fir_plot.m)
%       HN = firopt(TY, N, A, SF, FP, FS)
%	TY = 'lp', 'bp', 'bs', 'hp'
%       N = filter length
%       A = [Ap As] attenuation specs in dB
%       SF = sampling frequency (Hz)
%       FP=passband edge(s) Hz
%       FS=stopband edge(s) Hz
%
%	HWN returns coefficients of the LP prototype filter

% Author: Ashok Ambardar <[e-mail]>
% Date: 2/2/96 11:32AM
% Copyright (c) 1997 by Prentice-Hall, Inc.

%Fix length as needed by remez
n=n-1;

%COMPUTE RIPPLE & PREPARE FOR REMEZ
ap = a(1);
as = a(2);
%dp = [(10)^(0.05*ap)-1]/[(10)^(0.05*ap)+1];
dp=[1-(10)^(-0.05*ap)]/2;  % For measures from 0 dB
ds=(10)^(-0.05*as);
delt=1-dp;
dp=dp/delt;
ds=ds/delt;
k = ds/dp;
fp = fp/sf;
fs = fs/sf;

%%%%%%  NEW:   MAKE FREQUENCIES SYMMETRIC  %%%%%%%%%%%%%%%%%%%%%%%%
if ty < 3,
fpp=fp;
fss=fs;
else,
df1=abs(fp(1)-fs(1));
df2=abs(fs(2)-fp(2));
df=min(df1,df2);
fpp=0.5*abs(diff(fp));
fss=fpp+df;
if ty == 3
fs=[fp(1)-df fp(2)+df];  % New stopband
else
fs=[fp(1)+df fp(2)-df];  % New stopband
end
end
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

if ty == 1, % lowpass
   M = [1 1 0 0];
   F = 2*[0 fp fs 0.5];
   W = [k 1];

elseif ty == 2, % highpass
   M = [0 0 1 1];
   F = 2*[0 fs fp 0.5];
   W = [1 k];

elseif ty == 3, % bandpass
   M = [0 0 1 1 0 0];
   F = 2*[0 fs(1) fp(1) fp(2) fs(2) 0.5];
   W = [1 k 1];

else  % bandstop
   M = [1 1 0 0 1 1];
   F = 2*[0 fp(1) fs(1) fs(2) fp(2) 0.5];
   W = [k 1 k];
end

hwn = remez(n,F,M,W);
hwn = hwn.*(abs(hwn)>10*eps);