1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
|
// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) INRIA -
//
// 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 fr=freson(h)
[lhs,rhs]=argn(0);
[n,d]=h(["num","den"]);
if type(n)==1 then
n=poly(n,varn(d),"c");
end
if coeff(d,0)==0 then
error(msprintf(_("%s: Wrong value for input argument #%d: infinite gain at zero frequency.\n"),"freson",1))
end
//look for omega such that derivative of magn. is zero
niw=horner(n,%i*poly(0,"w"));
diw=horner(d,%i*poly(0,"w"));
niw=real(niw*conj(niw));diw=real(diw*conj(diw));
modul_d=derivat(niw/diw);w=roots(modul_d.num);
// get extreme points
k=find(imag(w)==0&real(w)>=0);
if k==[] then
fr=[];
g=[];
return
end
w=gsort(real(w(k)),"g","i");
//find maximums
wx=max(w)+0.5;
if horner(modul_d,wx)<0 then
w=w($:-2:1);
else
w=w($-1:-2:1);
end
fr=w/(2*%pi);
endfunction
|
