dfirwin.m

ADSP TOOLBOX: Version 2.0 and gui m-files

function hwn = dfirwin(ty,n,fc,samp,fp,fs,wind,p1)
% Impulse response for window-based design
% This will be used to find and plot the spectrum (see fir_plot.m)
%       HN = firwhb(TY,N,FC,WIND,P1)
%	TY = 'lp', 'bp', 'bs', 'hp'
%       N = filter length
%       FC=cutoff frequency (for LP and HP)
%       FC=[FC, F0] for BP and Bs (where F0 is center frequency
%	WIND = window name in quotes (DEFAULT: 'hamming')
%	P1 = parameter for Kaiser and Dolph(Cbeby) window
%       NOTE: For halfband design, N must be odd.
%       For window design, N ust be odd if ty=BS or window=dolph(cheby)
%
%	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.

[wp,ws,w3]=dfirlpp(ty,2*pi*fp,2*pi*fs,samp);

wc = 2*pi*fc;
n0 = fix(n/2);
n1 = 1:n0;
hwin = winwind(wind,n,p1);

if rem(n,2) == 1,
   h = sin(wc*n1)./n1/pi;
   h = [fliplr(h) wc/pi h];
else
   h = sin(wc*(n1-.5))./(n1-.5)/pi;
   h = [fliplr(h) h];
end

hw = h.*hwin;
if ty == 1, % lowpass
   hwn = hw;
end

if rem(n,2) == 1,
   nn = -n0:n0;
else
   nn = [-n0+.5:-.5 .5:n0-.5];
end

if ty == 2, % highpass
   hwn = hw.*((-1).^nn);
end

if ty == 3, % bandpass
   hwn = 2*cos(nn*w3).*hw;
end

if ty == 4, % bandstop
   hwn = -2*cos(nn*w3).*hw;
   hwn(n0+1) = 1+hwn(n0+1);
end

hwn = hwn.*(abs(hwn)>10*eps);
%hwn = hwn/sum(hwn);