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
62
|
/*****************************************************************************/
/*
* rrctime.c -- Square Root Raised Cosine Function (Time Domain).
*
* Copyright (C) 2001, 2002
* Thomas Sailer (t.sailer@alumni.ethz.ch)
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
*
*
*/
/*****************************************************************************/
#define _GNU_SOURCE
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <math.h>
#include <float.h>
#include "raisedcosine.h"
/* --------------------------------------------------------------------- */
/*
* see Huber: Trelliscodierung, S. 15, or ptolemy source code
*
* [ (4 alpha t) cos( pi (1+alpha) t) + sin (pi (1 - alpha)t) ] / [ (pi t) (1 - (4 alpha t)^2) ]
*/
double root_raised_cosine_time(double time, double alpha)
{
float opap, omap, at4, omat4sq;
if (fabs(alpha) < 1e-8)
return sinc(time);
if (fabs(time) < 1e-8)
return ((4.0 / M_PI) - 1.0) * alpha + 1.0;
opap = (1.0 + alpha) * M_PI;
omap = (1.0 - alpha) * M_PI;
at4 = alpha * time * 4;
omat4sq = 1 - at4 * at4;
if (fabs(omat4sq) < 1e-8)
return ((4.0 * alpha) * cos(opap * time) - at4 * opap * sin(opap * time) + omap * cos(omap * time)) / (1 - 3 * at4 * at4) * (1.0 / M_PI);
return (4.0 / M_PI) * alpha / omat4sq * (cos(opap * time) + sin(omap * time) / at4);
}
|
