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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_V2.1-en.txt
function [hzt,zt,gt]=trans(pd,zd,gd,tr_type,frq)
//hzt=trans(pd,zd,gd,tr_type,frq)
//macro for transforming standardized low-pass filter into
//one of the following filters:
// low-pass, high-pass, band-pass, stop-band.
// hz :input polynomial
// tr_type :type of transformation
// frq :frequency values
// hzt :output polynomial
//!
if and(argn(1)<>[1 3]) then
error(msprintf(gettext("%s: Wrong number of output arguments: %d or %d expected.\n"),"trans",1,3))
end
select argn(2)
case 3 then //trans(hz,tr_type,frq): filter given by a siso tranfer function
hz=pd
if typeof(hz)<>"rational" then
error(msprintf(_("%s: Wrong type for input argument #%d: rational fraction array expected.\n"),"trans",1))
end
if size(hz,"*")<>1 then
error(msprintf(_("%s: Wrong size for input argument #%d: A single input, single output system expected.\n"),"trans",1))
end
tr_type=zd;tr_pos=2;
frq=gd;frq_pos=3;
pd=roots(hz.den)
zd=roots(hz.num)
gd=coeff(hz.num,degree(hz.num))/coeff(hz.den,degree(hz.den))
case 5 then //trans(pd,zd,gd,tr_type,frq): filter given by zeros,poles and gain
if type(pd)<>1 then
error(msprintf(_("%s: Wrong type for input argument #%d: Array of floating point numbers expected.\n"),"trans",1))
end
if type(zd)<>1 then
error(msprintf(_("%s: Wrong type for input argument #%d: Array of floating point numbers expected.\n"),"trans",2))
end
if type(gd)<>1|size(gd,"*")<>1 then
error(msprintf(_("%s: Wrong size for input argument #%d: A scalar expected.\n"),"trans",3))
end
tr_pos=4;
frq_pos=5;
else
error(msprintf(_("%s: Wrong number of input arguments: %d or %d expected.\n"),"trans",3,5))
end
if and(tr_type<>["lp","hp","bp","sb"]) then
error(msprintf(_("%s: Wrong value for input argument #%d: Must be in the set {%s}.\n"),"trans",tr_pos,"''lp'',''hp'',''bp'',''sb''"))
end
if type(frq)<>1 then
error(msprintf(_("%s: Wrong type for input argument #%d: Array of floating point numbers expected.\n"),"trans",frq_pos))
end
if or(tr_type==["lp","hp"]) then
if and(size(frq,"*")<>[1,2]) then
error(msprintf(_("%s: Wrong size for input argument #%d: A scalar expected.\n"),"trans",frq_pos))
end
fu=frq(1)
else
if size(frq,"*")<>2 then
error(msprintf(_("%s: Wrong size for input argument #%d: A %d elements array expected.\n"),"trans",frq_pos,2))
end
fu=frq(1);fl=frq(2);
end
z=poly(0,"z");fc=.25;
//make filter type using all-pass change of variables
select tr_type
case "lp" then
alpha=sin(%pi*(fc-fu))/sin(%pi*(fc+fu));
num=z-alpha;
den=1-alpha*z;
case "hp" then
alpha=-cos(%pi*(fc-fu))/cos(%pi*(fc+fu));
num=-(1+alpha*z);
den=z+alpha;
case "bp" then
k=tan(%pi*fc)/tan(%pi*(fu-fl));
alpha=cos(%pi*(fu+fl))/cos(%pi*(fu-fl));
num=-((k+1)-2*alpha*k*z+(k-1)*z^2);
den=(k+1)*z^2-2*alpha*k*z+(k-1);
case "sb" then
k=tan(%pi*fc)*tan(%pi*(fu-fl));
alpha=cos(%pi*(fu+fl))/cos(%pi*(fu-fl));
num=(k+1)-2*alpha*z+(1-k)*z^2;
den=(k+1)*z^2-2*alpha*z+(1-k);
end
if tr_type == "lp" & fu == 0.25 then //no change of variables is necessary if user wants a low pass filter with cut off frequency of 0.25Hz.
pt=pd;
zt=zd;
gt=gd;
else
[pt,zt,gt]=bilt(pd,zd,gd,num,den);
end
if argn(1)==1 then
hzt=rlist(gt*real(poly(zt,"z")),real(poly(pt,"z")),"d");
else
hzt=pt(:)
zt=zt(:)
end
endfunction
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