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
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
|
/* -*- c++ -*- */
/*
* Copyright 2006,2010,2011 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* 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.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <digital_costas_loop_cc.h>
#include <gr_io_signature.h>
#include <gr_expj.h>
#include <gr_sincos.h>
#include <gr_math.h>
digital_costas_loop_cc_sptr
digital_make_costas_loop_cc (float loop_bw, int order
) throw (std::invalid_argument)
{
return gnuradio::get_initial_sptr(new digital_costas_loop_cc
(loop_bw, order));
}
digital_costas_loop_cc::digital_costas_loop_cc (float loop_bw, int order
) throw (std::invalid_argument)
: gr_sync_block ("costas_loop_cc",
gr_make_io_signature (1, 1, sizeof (gr_complex)),
gr_make_io_signature2 (1, 2, sizeof (gr_complex), sizeof(float))),
gri_control_loop(loop_bw, 1.0, -1.0),
d_order(order), d_phase_detector(NULL)
{
// Set up the phase detector to use based on the constellation order
switch(d_order) {
case 2:
d_phase_detector = &digital_costas_loop_cc::phase_detector_2;
break;
case 4:
d_phase_detector = &digital_costas_loop_cc::phase_detector_4;
break;
case 8:
d_phase_detector = &digital_costas_loop_cc::phase_detector_8;
break;
default:
throw std::invalid_argument("order must be 2, 4, or 8");
break;
}
}
float
digital_costas_loop_cc::phase_detector_8(gr_complex sample) const
{
/* This technique splits the 8PSK constellation into 2 squashed
QPSK constellations, one when I is larger than Q and one where
Q is larger than I. The error is then calculated proportionally
to these squashed constellations by the const K = sqrt(2)-1.
The signal magnitude must be > 1 or K will incorrectly bias
the error value.
Ref: Z. Huang, Z. Yi, M. Zhang, K. Wang, "8PSK demodulation for
new generation DVB-S2", IEEE Proc. Int. Conf. Communications,
Circuits and Systems, Vol. 2, pp. 1447 - 1450, 2004.
*/
float K = (sqrt(2.0) - 1);
if(fabsf(sample.real()) >= fabsf(sample.imag())) {
return ((sample.real()>0 ? 1.0 : -1.0) * sample.imag() -
(sample.imag()>0 ? 1.0 : -1.0) * sample.real() * K);
}
else {
return ((sample.real()>0 ? 1.0 : -1.0) * sample.imag() * K -
(sample.imag()>0 ? 1.0 : -1.0) * sample.real());
}
}
float
digital_costas_loop_cc::phase_detector_4(gr_complex sample) const
{
return ((sample.real()>0 ? 1.0 : -1.0) * sample.imag() -
(sample.imag()>0 ? 1.0 : -1.0) * sample.real());
}
float
digital_costas_loop_cc::phase_detector_2(gr_complex sample) const
{
return (sample.real()*sample.imag());
}
int
digital_costas_loop_cc::work (int noutput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
const gr_complex *iptr = (gr_complex *) input_items[0];
gr_complex *optr = (gr_complex *) output_items[0];
float *foptr = (float *) output_items[1];
bool write_foptr = output_items.size() >= 2;
float error;
gr_complex nco_out;
if (write_foptr) {
for (int i = 0; i < noutput_items; i++){
nco_out = gr_expj(-d_phase);
optr[i] = iptr[i] * nco_out;
error = (*this.*d_phase_detector)(optr[i]);
error = gr_branchless_clip(error, 1.0);
advance_loop(error);
phase_wrap();
frequency_limit();
foptr[i] = d_freq;
}
} else {
for (int i = 0; i < noutput_items; i++){
nco_out = gr_expj(-d_phase);
optr[i] = iptr[i] * nco_out;
error = (*this.*d_phase_detector)(optr[i]);
error = gr_branchless_clip(error, 1.0);
advance_loop(error);
phase_wrap();
frequency_limit();
}
}
return noutput_items;
}
|
