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/* -*- c++ -*- */
/*
* Copyright 2014,2018 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* SPDX-License-Identifier: GPL-3.0-or-later
*
*/
#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 * GR_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)
{
constexpr float alpha = 0.01;
constexpr float beta = alpha * alpha / 4.0;
const gr_complex* in = (const gr_complex*)input_items[0];
float* out = (float*)output_items[0];
float a_cos, a_sin;
float x;
gr_complex result, filtered;
for (int k = 0; k < noutput_items; k++) {
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::fast_cc_multiply(result, in[k], gr_complex(a_sin, a_cos));
out[k] = result.real();
// Update phase/freq error
filtered = d_afc.filter(result);
x = gr::fast_atan2f(filtered.imag(), filtered.real());
// avoid slamming filter with big transitions
if (x > M_PI_2)
x = M_PI_2;
else if (x < -M_PI_2)
x = -M_PI_2;
d_nco.adjust_phase(alpha * x);
d_nco.adjust_freq(beta * x);
}
return noutput_items;
}
} /* namespace dtv */
} /* namespace gr */
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