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/* -*- 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 <math.h>
#define M_TWOPI (2*M_PI)
digital_costas_loop_cc_sptr
digital_make_costas_loop_cc (float damping, float nat_freq,
int order
) throw (std::invalid_argument)
{
return gnuradio::get_initial_sptr(new digital_costas_loop_cc (damping,
nat_freq,
order));
}
digital_costas_loop_cc::digital_costas_loop_cc (float damping, float nat_freq,
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))),
d_max_freq(1.0), d_min_freq(-1.0), d_phase(0), d_freq(0.0),
d_nat_freq(nat_freq), d_damping(damping),
d_order(order), d_phase_detector(NULL)
{
// initialize gains from the natural freq and damping factors
update_gains();
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
{
float K = sqrt(2.0) - 1;
if(abs(sample.real()) >= abs(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());
}
void
digital_costas_loop_cc::set_natural_freq(float w)
{
d_nat_freq = w;
update_gains();
}
void
digital_costas_loop_cc::set_damping_factor(float eta)
{
d_damping = eta;
update_gains();
}
void
digital_costas_loop_cc::update_gains()
{
d_beta = d_nat_freq*d_nat_freq;
d_alpha = 2*d_damping*d_nat_freq;
}
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]);
if (error > 1)
error = 1;
else if (error < -1)
error = -1;
d_freq = d_freq + d_beta * error;
d_phase = d_phase + d_freq + d_alpha * error;
while(d_phase>M_TWOPI)
d_phase -= M_TWOPI;
while(d_phase<-M_TWOPI)
d_phase += M_TWOPI;
if (d_freq > d_max_freq)
d_freq = d_min_freq;
else if (d_freq < d_min_freq)
d_freq = d_max_freq;
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]);
if (error > 1)
error = 1;
else if (error < -1)
error = -1;
d_freq = d_freq + d_beta * error;
d_phase = d_phase + d_freq + d_alpha * error;
while(d_phase>M_TWOPI)
d_phase -= M_TWOPI;
while(d_phase<-M_TWOPI)
d_phase += M_TWOPI;
if (d_freq > d_max_freq)
d_freq = d_max_freq;
else if (d_freq < d_min_freq)
d_freq = d_min_freq;
}
}
return noutput_items;
}
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