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/* -*- c++ -*- */
/*
* Copyright 2006,2011 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.
*/
#ifndef INCLUDED_DIGITAL_COSTAS_LOOP_CC_H
#define INCLUDED_DIGITAL_COSTAS_LOOP_CC_H
#include <gr_sync_block.h>
#include <stdexcept>
#include <fstream>
/*! \brief A Costas loop carrier recovery module.
* \ingroup sync_blk
*
* The Costas loop locks to the center frequency of a signal and
* downconverts it to baseband. The second (order=2) order loop is
* used for BPSK where the real part of the output signal is the
* baseband BPSK signal and the imaginary part is the error
* signal. When order=4, it can be used for quadrature modulations
* where both I and Q (real and imaginary) are outputted.
*
* More details can be found online:
*
* J. Feigin, "Practical Costas loop design: Designing a simple and inexpensive
* BPSK Costas loop carrier recovery circuit," RF signal processing, pp. 20-36,
* 2002.
*
* http://rfdesign.com/images/archive/0102Feigin20.pdf
*
* \param alpha the loop gain used for phase adjustment
* \param beta the loop gain for frequency adjustments
* \param max_freq the maximum frequency deviation (radians/sample) the loop can handle
* \param min_freq the minimum frequency deviation (radians/sample) the loop can handle
* \param order the loop order, either 2 or 4
*/
class digital_costas_loop_cc;
typedef boost::shared_ptr<digital_costas_loop_cc> digital_costas_loop_cc_sptr;
digital_costas_loop_cc_sptr
digital_make_costas_loop_cc (float damping, float nat_freq,
int order
) throw (std::invalid_argument);
/*!
* \brief Carrier tracking PLL for QPSK
* \ingroup sync_blk
* input: complex; output: complex
* <br>The Costas loop can have two output streams:
* stream 1 is the baseband I and Q;
* stream 2 is the normalized frequency of the loop
*
* \p order must be 2 or 4.
*/
class digital_costas_loop_cc : public gr_sync_block
{
friend digital_costas_loop_cc_sptr
digital_make_costas_loop_cc (float damping, float nat_freq,
int order
) throw (std::invalid_argument);
float d_alpha, d_beta, d_max_freq, d_min_freq, d_phase, d_freq;
float d_nat_freq, d_damping;
int d_order;
digital_costas_loop_cc (float damping, float nat_freq,
int order
) throw (std::invalid_argument);
/*! \brief update the system gains from omega and eta
*
* This function updates the system gains based on the natural
* frequency (omega) and damping factor (eta) of the system.
* These two factors can be set separately through their own
* set functions.
*
* These equations are summarized nicely in this paper from Berkeley:
* http://www.complextoreal.com/chapters/pll.pdf
*/
void update_gains();
/*! \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
/*! \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
/*! \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
float (digital_costas_loop_cc::*d_phase_detector)(gr_complex sample) const;
public:
void set_natural_freq(float w);
void set_damping_factor(float eta);
/*! \brief get the first order gain
*
*/
float alpha() const { return d_alpha; }
/*! \brief get the second order gain
*
*/
float beta() const { return d_beta; }
int work (int noutput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items);
/*! \brief returns the current NCO frequency in radians/sample
*
*/
float freq() const { return d_freq; }
};
#endif
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