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// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) INRIA - 1988 - C. Bunks
//
// This file must be used under the terms of the CeCILL.
// This source file is licensed as described in the file COPYING, which
// you should have received as part of this distribution. The terms
// are also available at
// http://www.cecill.info/licences/Licence_CeCILL_V2-en.txt
function [wft,wfm,fr]=wfir(ftype,forder,cfreq,wtype,fpar)
//[wft,wfm,fr]=wfir(ftype,forder,cfreq,wtype,fpar)
//Macro which makes linear-phase, FIR low-pass, band-pass,
//high-pass, and stop-band filters
//using the windowing technique.
//Works interactively if called with no arguments.
// ftype :Filter type ('lp','hp','bp','sb')
// forder :Filter order (pos integer)(odd for ftype='hp' or 'sb')
// cfreq :2-vector of cutoff frequencies (0<cfreq(1),cfreq(2)<.5)
// :only cfreq(1) is used when ftype='lp' or 'hp'
// wtype :Window type ('re','tr','hm','hn','kr','ch')
// fpar :2-vector of window parameters
// : Kaiser window: fpar(1)>0 fpar(2)=0
// : Chebyshev window: fpar(1)>0 fpar(2)<0 or
// : fpar(1)<0 0<fpar(2)<.5
// wft :Time domain filter coefficients
// wfm :Frequency domain filter response on the grid fr
// fr :Frequency grid
//!
wft=[];wfm=[];fr=[]
//check arguments of macro call
[lhs,rhs]=argn(0);
//if macro called with no arguments query user for values
if rhs<=0 then,
//Query user for filter type and filter length
nc=x_choose([gettext('low pass');
gettext('high pass');
gettext('band pass');
gettext('stop band')],gettext('Choose type of filter to be designed'))
//Select filter type and Query user for cut-off frequencies
flag=0;
select nc
case 1 then //low pass
[ok,fl,forder]=scicos_getvalue(gettext('Input filter characteristics'),..
[gettext('cut-off frequency (0.<frequ<.5):');
gettext('filter length')],..
list('vec',1,'vec',1),[' ';' '])
ftype='lp'
fh=0;
case 2 then //high pass
[ok,fl,forder]=scicos_getvalue(gettext('Input filter characteristics'),..
[gettext('cut-off frequency (0.<frequ<.5):');
gettext('filter length (odd value)')],..
list('vec',1,'vec',1),[' ';' '])
fh=0;
flag=1;
ftype='hp'
case 3 then //band pass
[ok,fl,fh,forder]=scicos_getvalue(gettext('Input filter characteristics'),..
[gettext('low cut-off frequency (0.<flow<.5):');
gettext('high cut-off frequency (0.<flow<fhi<.5):');
gettext('filter length')],..
list('vec',1,'vec',1,'vec',1),[' ';' ';' '])
ftype='bp'
case 4 then //stop band
[ok,fl,fh,forder]=scicos_getvalue(gettext('Input filter characteristics'),..
[gettext('low cut-off frequency (0.<flow<.5):');
gettext('high cut-off frequency (0.<flow<fhi<.5):');
gettext('filter length (odd value)')],..
list('vec',1,'vec',1,'vec',1),[' ';' ';' '])
flag=1;
ftype='sb'
else
return
end
if flag==1 then
if forder-2*int(forder/2)==0 then
messagebox([gettext('Even length high pass and stop band filters not allowed');
gettext('---Filter order is being incremented by 1')],"modal","error");
forder=forder+1;
end
end
//Query user for window type and window parameters
nc=x_choose([gettext('Kaiser');
gettext('Chebyshev');
gettext('Rectangular');
gettext('Triangular');
gettext('Hamming') ],gettext('Input window type'))
select nc
case 1 then
wtype='kr'
[ok,Beta]=scicos_getvalue(gettext('Input window characteristics'),..
['beta>0'],list('vec',1),' ')
fpar(1)=Beta
fpar(2)=0;
case 2 then
wtype='ch'
[ok,name,value]=scicos_getvalue([gettext('Input window characteristics:');
' ';
gettext('dp (dp>0) : the maximum value of the window side-lobe height');
gettext('df (0<df<.5): the width of the window main lobe')
' ';
gettext('only one of this two values is to be defined,')
gettext('the other one is automaticaly deduced')],..
[gettext('name of specified value');
gettext('value')],list('str',-1,'vec',1),['dp','0.3'])
if part(name,1:2)=='dp' then
fpar=[value,-1]
elseif part(name,1:2)=='df' then
fpar=[-1,value]
else
messagebox(gettext('Incorrect parameter name entered'),"modal","error");
return
end
case 3 then
wtype='re'
fpar=[0 0];
case 4 then
wtype='tr'
fpar=[0 0];
case 5 then
wtype='hm'
fpar=[0 0];
case 6 then
wtype='hn'
fpar=[0 0];
else
return
end
else
fl=cfreq(1);
fh=cfreq(2);
end,
//Calculate window coefficients
[win_l,cwp]=window(wtype,forder,fpar);
[dummy,forder]=size(win_l);
//Get forder samples of the appropriate filter type
hfilt=ffilt(ftype,forder,fl,fh);
//Multiply window with sinc function
wft=win_l.*hfilt;
//Calculate frequency response of the windowed filter
[wfm,fr]=frmag(wft,256);
endfunction
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