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/* -*- c++ -*- */
/*
* Copyright 2006,2011,2012,2014 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* SPDX-License-Identifier: GPL-3.0-or-later
*
*/
#ifndef INCLUDED_DIGITAL_COSTAS_LOOP_CC_IMPL_H
#define INCLUDED_DIGITAL_COSTAS_LOOP_CC_IMPL_H
#include <gnuradio/digital/costas_loop_cc.h>
namespace gr {
namespace digital {
class costas_loop_cc_impl : public costas_loop_cc
{
private:
float d_error;
float d_noise;
bool d_use_snr;
int d_order;
/*! \brief the phase detector circuit for 8th-order PSK loops.
*
* \param sample complex sample
* \return the phase error
*/
float phase_detector_8(gr_complex sample) const // for 8PSK
{
/* 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.
*/
const float K = (sqrtf(2.0) - 1);
if (fabsf(sample.real()) >= fabsf(sample.imag())) {
return ((sample.real() > 0.0f ? 1.0f : -1.0f) * sample.imag() -
(sample.imag() > 0.0f ? 1.0f : -1.0f) * sample.real() * K);
} else {
return ((sample.real() > 0.0f ? 1.0f : -1.0f) * sample.imag() * K -
(sample.imag() > 0.0f ? 1.0f : -1.0f) * sample.real());
}
};
/*! \brief the phase detector circuit for fourth-order loops.
*
* \param sample complex sample
* \return the phase error
*/
float phase_detector_4(gr_complex sample) const // for QPSK
{
return ((sample.real() > 0.0f ? 1.0f : -1.0f) * sample.imag() -
(sample.imag() > 0.0f ? 1.0f : -1.0f) * sample.real());
};
/*! \brief the phase detector circuit for second-order loops.
*
* \param sample a complex sample
* \return the phase error
*/
float phase_detector_2(gr_complex sample) const // for BPSK
{
return (sample.real() * sample.imag());
}
/*! \brief the phase detector circuit for 8th-order PSK
* loops. Uses tanh instead of slicing and the noise estimate
* from the message port to estimated SNR of the samples.
*
* \param sample complex sample
* \return the phase error
*/
float phase_detector_snr_8(gr_complex sample) const // for 8PSK
{
const float K = (sqrtf(2.0) - 1.0);
const float snr = std::norm(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()));
}
};
/*! \brief the phase detector circuit for fourth-order
* loops. Uses tanh instead of slicing and the noise estimate
* from the message port to estimated SNR of the samples.
*
* \param sample complex sample
* \return the phase error
*/
float phase_detector_snr_4(gr_complex sample) const // for QPSK
{
const float snr = std::norm(sample) / d_noise;
return ((blocks::tanhf_lut(snr * sample.real()) * sample.imag()) -
(blocks::tanhf_lut(snr * sample.imag()) * sample.real()));
};
/*! \brief the phase detector circuit for second-order
* loops. Uses tanh instead of slicing and the noise estimate
* from the message port to estimated SNR of the samples.
*
* \param sample a complex sample
* \return the phase error
*/
float phase_detector_snr_2(gr_complex sample) const // for BPSK
{
const float snr = std::norm(sample) / d_noise;
return blocks::tanhf_lut(snr * sample.real()) * sample.imag();
};
public:
costas_loop_cc_impl(float loop_bw, unsigned int order, bool use_snr = false);
~costas_loop_cc_impl() override;
float error() const override { return d_error; };
void handle_set_noise(pmt::pmt_t msg);
void setup_rpc() override;
int work(int noutput_items,
gr_vector_const_void_star& input_items,
gr_vector_void_star& output_items) override;
};
} /* namespace digital */
} /* namespace gr */
#endif /* INCLUDED_DIGITAL_COSTAS_LOOP_CC_IMPL_H */
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