clock_recovery_mm_cc.h

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/* -*- c++ -*- */
/*
 * Copyright 2004,2011,2012 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.
 */
 
#ifndef INCLUDED_DIGITAL_CLOCK_RECOVERY_MM_CC_H
#define INCLUDED_DIGITAL_CLOCK_RECOVERY_MM_CC_H
 
#include <gnuradio/block.h>
#include <gnuradio/digital/api.h>
 
namespace gr {
namespace digital {
 
/*!
 * \brief Mueller and Müller (M&M) based clock recovery block with complex input, complex
 * output. \ingroup synchronizers_blk
 *
 * \details
 * This implements the Mueller and Müller (M&M) discrete-time
 * error-tracking synchronizer.
 *
 * The peak to peak input signal amplitude must be symmetrical
 * about zero, as the M&M timing error detector (TED) is a
 * decision directed TED, and this block uses a symbol decision
 * slicer referenced at zero.
 *
 * The input signal peak amplitude should be controlled to a
 * consistent level (e.g. +/- 1.0) before this block to achieve
 * consistent results for given gain settings; as the TED's output
 * error signal is directly affected by the input amplitude.
 *
 * The input signal must have peaks in order for the TED to output
 * a correct error signal. If the input signal pulses do not have
 * peaks (e.g. rectangular pulses) the input signal should be
 * conditioned with a matched pulse filter or other appropriate
 * filter to peak the input pulses. For a rectangular base pulse
 * that is N samples wide, the matched filter taps would be
 * [1.0/float(N)]*N, or in other words a moving average over N
 * samples.
 *
 * This block will output samples at a rate of one sample per
 * recovered symbol, and is thus not outputting at a constant rate.
 *
 * Output symbols are not a subset of input, but may be interpolated.
 *
 * The complex version here is based on: Modified Mueller and
 * Muller clock recovery circuit:
 *
 *    G. R. Danesfahani, T.G. Jeans, "Optimisation of modified Mueller
 *    and Muller algorithm," Electronics Letters, Vol. 31, no. 13, 22
 *    June 1995, pp. 1032 - 1033.
 */
class DIGITAL_API clock_recovery_mm_cc : virtual public block
{
public:
    // gr::digital::clock_recovery_mm_cc::sptr
    typedef boost::shared_ptr<clock_recovery_mm_cc> sptr;
 
    /*!
     * Make a M&M clock recovery block.
     *
     * \param omega Initial estimate of samples per symbol
     * \param gain_omega Gain setting for omega update loop
     * \param mu Initial estimate of phase of sample
     * \param gain_mu Gain setting for mu update loop
     * \param omega_relative_limit limit on omega
     */
    static sptr make(float omega,
                     float gain_omega,
                     float mu,
                     float gain_mu,
                     float omega_relative_limit);
 
    virtual float mu() const = 0;
    virtual float omega() const = 0;
    virtual float gain_mu() const = 0;
    virtual float gain_omega() const = 0;
 
    virtual void set_verbose(bool verbose) = 0;
    virtual void set_gain_mu(float gain_mu) = 0;
    virtual void set_gain_omega(float gain_omega) = 0;
    virtual void set_mu(float mu) = 0;
    virtual void set_omega(float omega) = 0;
};
 
} /* namespace digital */
} /* namespace gr */
 
#endif /* INCLUDED_DIGITAL_CLOCK_RECOVERY_MM_CC_H */