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/* -*- c++ -*- */
/*
* Copyright 2006,2011,2012,2014 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 <gnuradio/digital/api.h>
#include <gnuradio/blocks/control_loop.h>
#include <gnuradio/sync_block.h>
namespace gr {
namespace digital {
/*!
* \brief A Costas loop carrier recovery module.
* \ingroup synchronizers_blk
*
* \details
* The Costas loop locks to the center frequency of a signal and
* downconverts it to baseband.
*
* \li When order=2: used for BPSK where the real part of the
* output signal is the baseband BPSK signal and the imaginary
* part is the error signal.
*
* \li When order=4: can be used for QPSK where both I and Q (real
* and imaginary) are outputted.
*
* \li When order=8: used for 8PSK.
*
* 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
*
* The Costas loop can have two output streams:
* \li stream 1 (required) is the baseband I and Q;
* \li stream 2 (optional) is the normalized frequency of the loop
*
* There is a single optional message input:
* \li noise: A noise floor estimate used to calculate the SNR of a sample.
*/
class DIGITAL_API costas_loop_cc
: virtual public sync_block,
virtual public blocks::control_loop
{
public:
// gr::digital::costas_loop_cc::sptr
typedef boost::shared_ptr<costas_loop_cc> sptr;
/*!
* Make a Costas loop carrier recovery block.
*
* \param loop_bw internal 2nd order loop bandwidth (~ 2pi/100)
* \param order the loop order, either 2, 4, or 8
* \param use_snr Use or ignore SNR estimates (from noise message port)
* in measurements; also uses tanh instead of slicing.
*/
static sptr make(float loop_bw, int order, bool use_snr=false);
/*!
* Returns the current value of the loop error.
*/
virtual float error() const = 0;
};
} /* namespace digital */
} /* namespace gr */
#endif /* INCLUDED_DIGITAL_COSTAS_LOOP_CC_H */
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