cpmmod_bc.h

Go to the documentation of this file.

/* -*- c++ -*- */
/*
 * Copyright 2010,2012 Free Software Foundation, Inc.
 *
 * This file is part of GNU Radio
 *
 * SPDX-License-Identifier: GPL-3.0-or-later
 *
 */
 
#ifndef INCLUDED_DIGITAL_CPMMOD_BC_H
#define INCLUDED_DIGITAL_CPMMOD_BC_H
 
#include <gnuradio/analog/cpm.h>
#include <gnuradio/digital/api.h>
#include <gnuradio/hier_block2.h>
 
namespace gr {
namespace digital {
 
/*!
 * \brief Generic CPM modulator
 * \ingroup modulators_blk
 *
 * \details
 * Examples:
 * - Setting h = 0.5, L = 1, type = LREC yields MSK.
 * - Setting h = 0.5, type = GAUSSIAN and beta = 0.3 yields GMSK
 *           as used in GSM.
 *
 * The input of this block are symbols from an M-ary alphabet
 * +/-1, +/-3, ..., +/-(M-1). Usually, M = 2 and therefore, the
 * valid inputs are +/-1.
 * The modulator will silently accept any other inputs, though.
 * The output is the phase-modulated signal.
 */
class DIGITAL_API cpmmod_bc : virtual public hier_block2
{
public:
    // gr::digital::cpmmod_bc::sptr
    typedef std::shared_ptr<cpmmod_bc> sptr;
 
    /*!
     * Make CPM modulator block.
     *
     * \param type The modulation type. Can be one of LREC, LRC, LSRC, TFM
     *             or GAUSSIAN. See gr_cpm::phase_response() for a
     *             detailed description.
     * \param h The modulation index. \f$ h \cdot \pi\f$ is the maximum
     *          phase change that can occur between two symbols, i.e., if
     *          you only send ones, the phase will increase by \f$ h \cdot
     *          \pi\f$ every \p samples_per_sym samples. Set this to 0.5
     *          for Minimum Shift Keying variants.
     * \param samples_per_sym Samples per symbol.
     * \param L The length of the phase duration in symbols. For L=1, this
     *          yields full- response CPM symbols, for L > 1,
     *          partial-response.
     * \param beta For LSRC, this is the rolloff factor. For Gaussian
     *             pulses, this is the 3 dB time-bandwidth product.
     */
    static sptr make(analog::cpm::cpm_type type,
                     float h,
                     int samples_per_sym,
                     int L,
                     double beta = 0.3);
 
    /*!
     * Make GMSK modulator block.
     *
     * The type is GAUSSIAN and the modulation index for GMSK is
     * 0.5. This are populated automatically by this factory
     * function.
     *
     * \param samples_per_sym Samples per symbol.
     * \param L The length of the phase duration in symbols. For L=1, this
     *          yields full- response CPM symbols, for L > 1,
     *          partial-response.
     * \param beta For LSRC, this is the rolloff factor. For Gaussian
     *             pulses, this is the 3 dB time-bandwidth product.
     */
    static sptr make_gmskmod_bc(int samples_per_sym = 2, int L = 4, double beta = 0.3);
 
    //! Return the phase response FIR taps
    virtual std::vector<float> taps() const = 0;
 
    //! Return the type of CPM modulator
    virtual int type() const = 0;
 
    //! Return the modulation index of the modulator.
    virtual float index() const = 0;
 
    //! Return the number of samples per symbol
    virtual int samples_per_sym() const = 0;
 
    //! Return the length of the phase duration (in symbols)
    virtual int length() const = 0;
 
    //! Return the value of beta for the modulator
    virtual double beta() const = 0;
};
 
} /* namespace digital */
} /* namespace gr */
 
#endif /* INCLUDED_DIGITAL_CPMMOD_BC_H */