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
|
/* -*- c++ -*- */
/*
* Copyright 2014 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 "atsc_fpll_impl.h"
#include <gnuradio/io_signature.h>
#include <gnuradio/math.h>
#include <gnuradio/sincos.h>
namespace gr {
namespace dtv {
atsc_fpll::sptr
atsc_fpll::make(float rate)
{
return gnuradio::get_initial_sptr
(new atsc_fpll_impl(rate));
}
atsc_fpll_impl::atsc_fpll_impl(float rate)
: sync_block("dtv_atsc_fpll",
io_signature::make(1, 1, sizeof(gr_complex)),
io_signature::make(1, 1, sizeof(float)))
{
d_afc.set_taps(1.0-exp(-1.0/rate/5e-6));
d_nco.set_freq((-3e6 + 0.309e6)/rate*2*M_PI);
d_nco.set_phase(0.0);
}
atsc_fpll_impl::~atsc_fpll_impl()
{
}
int
atsc_fpll_impl::work(int noutput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
const gr_complex *in = (const gr_complex *)input_items[0];
float *out = (float *)output_items[0];
for (int k = 0; k < noutput_items; k++) {
float a_cos, a_sin;
d_nco.step(); // increment phase
d_nco.sincos(&a_sin, &a_cos); // compute cos and sin
// Mix out carrier and output I-only signal
gr_complex result = in[k]*gr_complex(a_sin, a_cos);
out[k] = result.real();
// Update phase/freq error
gr_complex filtered = d_afc.filter(result);
float x = gr::fast_atan2f(filtered.imag(), filtered.real());
// avoid slamming filter with big transitions
static const float limit = M_PI/2.0;
if (x > limit)
x = limit;
else if (x < -limit)
x = -limit;
static const float alpha = 0.0002;
static const float beta = alpha*alpha/4.0;
d_nco.adjust_phase(alpha*x);
d_nco.adjust_freq(beta*x);
}
return noutput_items;
}
} /* namespace dtv */
} /* namespace gr */
|
