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
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
|
// 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 an=remezb(nc,fg,ds,wt)
//an=remezb(nc,fg,ds,wt)
//Minimax approximation of a frequency domain
//magnitude response. The approximation takes
//the form
//
// h = sum[a(n)cos(wn)]
//
//for n=0,1,...,nc. An FIR, linear-phase filter
//can be obtained from the output of the macro
//by using the following Scilab commands
//
// hn(1:nc-1)=an(nc:-1:2)/2;
// hn(nc)=an(1);
// hn(nc+1:2*nc-1)=an(2:nc)/2;
//
// nc :Number of cosine functions
// fg :Grid of frequency points in [0,.5)
// ds :Desired magnitude on grid fg
// wt :Weighting function on error on grid fg
// an :Cosine filter coefficients
//!
//get frequency grid size
ngrid=max(size(fg));
//check for errors in input
if min(fg)<0|max(fg)>0.5 then
error(msprintf(gettext("%s: Wrong value for input argument #%d: Must be in the interval [%s, %s].\n"),"remezb",2,"0","0.5"));
end,
dsize=max(size(ds));
wsize=max(size(wt));
if dsize<>ngrid then
error(msprintf(gettext("%s: Incompatible input arguments #%d and #%d: Same sizes expected.\n"),"remezb",2,3));
end,
if wsize<>ngrid then
error(msprintf(gettext("%s: Incompatible input arguments #%d and #%d: Same sizes expected.\n"),"remezb",2,4));
end,
//set up the initial guess for the extremal frequencies
iext=round(1:ngrid/nc:ngrid);
iext(nc+1)=ngrid;
iext(nc+2)=ngrid;
//call remez.f
an=remez(iext,ds,fg,wt);
an=an(1:nc)
endfunction
|
