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urh/doc/costas_loop.cc
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2016-04-01 21:53:35 +02:00

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/* -*- c++ -*- */
/*
* Copyright 2006,2010-2012 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 "costas_loop_cc_impl.h"
#include <gnuradio/io_signature.h>
#include <gnuradio/expj.h>
#include <gnuradio/sincos.h>
#include <gnuradio/math.h>
#include <boost/format.hpp>
namespace gr {
namespace digital {
costas_loop_cc::sptr
costas_loop_cc::make(float loop_bw, int order, bool use_snr)
{
return gnuradio::get_initial_sptr
(new costas_loop_cc_impl(loop_bw, order, use_snr));
}
costas_loop_cc_impl::costas_loop_cc_impl(float loop_bw, int order, bool use_snr)
: sync_block("costas_loop_cc",
io_signature::make(1, 1, sizeof(gr_complex)),
io_signature::make2(1, 2, sizeof(gr_complex), sizeof(float))),
blocks::control_loop(loop_bw, 1.0, -1.0),
d_order(order), d_error(0), d_noise(1.0), d_phase_detector(NULL)
{
// Set up the phase detector to use based on the constellation order
switch(d_order) {
case 2:
if(use_snr)
d_phase_detector = &costas_loop_cc_impl::phase_detector_snr_2;
else
d_phase_detector = &costas_loop_cc_impl::phase_detector_2;
break;
case 4:
if(use_snr)
d_phase_detector = &costas_loop_cc_impl::phase_detector_snr_4;
else
d_phase_detector = &costas_loop_cc_impl::phase_detector_4;
break;
case 8:
if(use_snr)
d_phase_detector = &costas_loop_cc_impl::phase_detector_snr_8;
else
d_phase_detector = &costas_loop_cc_impl::phase_detector_8;
break;
default:
throw std::invalid_argument("order must be 2, 4, or 8");
break;
}
message_port_register_in(pmt::mp("noise"));
set_msg_handler(
pmt::mp("noise"),
boost::bind(&costas_loop_cc_impl::handle_set_noise,
this, _1));
}
costas_loop_cc_impl::~costas_loop_cc_impl()
{
}
float
costas_loop_cc_impl::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
costas_loop_cc_impl::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
costas_loop_cc_impl::phase_detector_2(gr_complex sample) const
{
return (sample.real()*sample.imag());
}
float
costas_loop_cc_impl::phase_detector_snr_8(gr_complex sample) const
{
float K = (sqrt(2.0) - 1);
float snr = abs(sample)*abs(sample) / d_noise;
if(fabsf(sample.real()) >= fabsf(sample.imag())) {
return ((blocks::tanhf_lut(snr*sample.real()) * sample.imag()) -
(blocks::tanhf_lut(snr*sample.imag()) * sample.real() * K));
}
else {
return ((blocks::tanhf_lut(snr*sample.real()) * sample.imag() * K) -
(blocks::tanhf_lut(snr*sample.imag()) * sample.real()));
}
}
float
costas_loop_cc_impl::phase_detector_snr_4(gr_complex sample) const
{
float snr = abs(sample)*abs(sample) / d_noise;
return ((blocks::tanhf_lut(snr*sample.real()) * sample.imag()) -
(blocks::tanhf_lut(snr*sample.imag()) * sample.real()));
}
float
costas_loop_cc_impl::phase_detector_snr_2(gr_complex sample) const
{
float snr = abs(sample)*abs(sample) / d_noise;
return blocks::tanhf_lut(snr*sample.real()) * sample.imag();
}
float
costas_loop_cc_impl::error() const
{
return d_error;
}
void
costas_loop_cc_impl::handle_set_noise(pmt::pmt_t msg)
{
if(pmt::is_real(msg)) {
d_noise = pmt::to_double(msg);
d_noise = powf(10.0f, d_noise/10.0f);
}
}
int
costas_loop_cc_impl::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;
gr_complex nco_out;
std::vector<tag_t> tags;
get_tags_in_range(tags, 0, nitems_read(0),
nitems_read(0)+noutput_items,
pmt::intern("phase_est"));
if(write_foptr) {
for(int i = 0; i < noutput_items; i++) {
if(tags.size() > 0) {
if(tags[0].offset-nitems_read(0) == (size_t)i) {
d_phase = (float)pmt::to_double(tags[0].value);
tags.erase(tags.begin());
}
}
nco_out = gr_expj(-d_phase);
optr[i] = iptr[i] * nco_out;
d_error = (*this.*d_phase_detector)(optr[i]);
d_error = gr::branchless_clip(d_error, 1.0);
advance_loop(d_error);
phase_wrap();
frequency_limit();
foptr[i] = d_freq;
}
}
else {
for(int i = 0; i < noutput_items; i++) {
if(tags.size() > 0) {
if(tags[0].offset-nitems_read(0) == (size_t)i) {
d_phase = (float)pmt::to_double(tags[0].value);
tags.erase(tags.begin());
}
}
nco_out = gr_expj(-d_phase);
optr[i] = iptr[i] * nco_out;
d_error = (*this.*d_phase_detector)(optr[i]);
d_error = gr::branchless_clip(d_error, 1.0);
advance_loop(d_error);
phase_wrap();
frequency_limit();
}
}
return noutput_items;
}
void
costas_loop_cc_impl::setup_rpc()
{
#ifdef GR_CTRLPORT
// Getters
add_rpc_variable(
rpcbasic_sptr(new rpcbasic_register_get<costas_loop_cc, float>(
alias(), "error",
&costas_loop_cc::error,
pmt::mp(-2.0f), pmt::mp(2.0f), pmt::mp(0.0f),
"", "Error signal of loop", RPC_PRIVLVL_MIN,
DISPTIME | DISPOPTSTRIP)));
add_rpc_variable(
rpcbasic_sptr(new rpcbasic_register_get<control_loop, float>(
alias(), "frequency",
&control_loop::get_frequency,
pmt::mp(0.0f), pmt::mp(2.0f), pmt::mp(0.0f),
"", "Frequency Est.", RPC_PRIVLVL_MIN,
DISPTIME | DISPOPTSTRIP)));
add_rpc_variable(
rpcbasic_sptr(new rpcbasic_register_get<control_loop, float>(
alias(), "phase",
&control_loop::get_phase,
pmt::mp(0.0f), pmt::mp(2.0f), pmt::mp(0.0f),
"", "Phase Est.", RPC_PRIVLVL_MIN,
DISPTIME | DISPOPTSTRIP)));
add_rpc_variable(
rpcbasic_sptr(new rpcbasic_register_get<control_loop, float>(
alias(), "loop_bw",
&control_loop::get_loop_bandwidth,
pmt::mp(0.0f), pmt::mp(2.0f), pmt::mp(0.0f),
"", "Loop bandwidth", RPC_PRIVLVL_MIN,
DISPTIME | DISPOPTSTRIP)));
// Setters
add_rpc_variable(
rpcbasic_sptr(new rpcbasic_register_set<control_loop, float>(
alias(), "loop bw",
&control_loop::set_loop_bandwidth,
pmt::mp(0.0f), pmt::mp(1.0f), pmt::mp(0.0f),
"", "Loop bandwidth",
RPC_PRIVLVL_MIN, DISPNULL)));
#endif /* GR_CTRLPORT */
}
} /* namespace digital */
} /* namespace gr */
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