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
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
|
/* -*- c++ -*- */
/*
* Copyright 2010,2012 Free Software Foundation, Inc.
*
* GNU Radio 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 3, or (at your option)
* any later version.
*
* GNU Radio 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 GNU Radio; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#ifndef INCLUDED_ANALOG_CPM_H
#define INCLUDED_ANALOG_CPM_H
#include <gnuradio/analog/api.h>
#include <vector>
namespace gr {
namespace analog {
/*! \brief Return the taps for an interpolating FIR filter
* (gr::filter::interp_fir_filter_fff).
*/
class ANALOG_API cpm
{
public:
enum cpm_type { LRC, LSRC, LREC, TFM, GAUSSIAN, GENERIC = 999 };
/*! \brief Return the taps for an interpolating FIR filter
* (gr::filter::interp_fir_filter_fff).
*
* \details
* These taps represent the phase response \f$g(k)\f$ for use in a CPM modulator,
* see also gr_cpmmod_bc.
*
* \param type The CPM type (Rectangular, Raised Cosine,
* Spectral Raised Cosine, Tamed FM or Gaussian).
* \param samples_per_sym Samples per symbol.
* \param L The length of the phase response in symbols.
* \param beta For Spectral Raised Cosine, this is the rolloff
* factor. For Gaussian phase responses, this the
* 3dB-time-bandwidth product. For all other cases,
* it is ignored.
*
* Output: returns a vector of length \a K = \p samples_per_sym
* x \p L. This can be used directly in an
* interpolating FIR filter such as
* gr_interp_fir_filter_fff with interpolation factor \p
* samples_per_sym.
*
* All phase responses are normalised s.t. \f$ \sum_{k=0}^{K-1}
* g(k) = 1\f$; this will cause a maximum phase change of \f$ h
* \cdot \pi\f$ between two symbols, where \a h is the
* modulation index.
*
* The following phase responses can be generated:
* - LREC: Rectangular phase response.
* - LRC: Raised cosine phase response, looks like 1 - cos(x).
* - LSRC: Spectral raised cosine. This requires a rolloff factor beta.
* The phase response is the Fourier transform of raised cosine
* function.
* - TFM: Tamed frequency modulation. This scheme minimizes phase change for
* rapidly varying input symbols.
* - GAUSSIAN: A Gaussian phase response. For a modulation index h = 1/2, this
* results in GMSK.
*
* A short description of all these phase responses can be found in [1].
*
* [1]: Anderson, Aulin and Sundberg; Digital Phase Modulation
*/
static std::vector<float> phase_response(cpm_type type,
unsigned samples_per_sym,
unsigned L,
double beta = 0.3);
};
} // namespace analog
} // namespace gr
#endif /* INCLUDED_ANALOG_CPM_H */
|
