GNU Radio 3.6.5.1 C++ API
cpm.h
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/* -*- c++ -*- */
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/*
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* Copyright 2010,2012 Free Software Foundation, Inc.
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*
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* GNU Radio is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 3, or (at your option)
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* any later version.
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*
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* GNU Radio is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with GNU Radio; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*/
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#ifndef INCLUDED_ANALOG_CPM_H
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#define INCLUDED_ANALOG_CPM_H
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#include <
analog/api.h
>
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#include <vector>
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namespace
gr {
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namespace
analog {
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class
ANALOG_API
cpm
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{
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public
:
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enum
cpm_type
{
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LRC
,
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LSRC
,
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LREC
,
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TFM
,
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GAUSSIAN
,
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GENERIC = 999
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};
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/*! \brief Return the taps for an interpolating FIR filter (gr_interp_fir_filter_fff).
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*
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* \details
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* These taps represent the phase response \f$g(k)\f$ for use in a CPM modulator,
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* see also gr_cpmmod_bc.
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*
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* \param type The CPM type (Rectangular, Raised Cosine, Spectral Raised Cosine,
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* Tamed FM or Gaussian).
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* \param samples_per_sym Samples per symbol.
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* \param L The length of the phase response in symbols.
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* \param beta For Spectral Raised Cosine, this is the rolloff factor. For Gaussian
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* phase responses, this the 3dB-time-bandwidth product. For all other
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* cases, it is ignored.
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*
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* Output: returns a vector of length \a K = \p samples_per_sym x \p L.
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* This can be used directly in an interpolating FIR filter such as
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* gr_interp_fir_filter_fff with interpolation factor \p samples_per_sym.
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*
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* All phase responses are normalised s.t. \f$ \sum_{k=0}^{K-1} g(k) = 1\f$; this will cause
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* a maximum phase change of \f$ h \cdot \pi\f$ between two symbols, where \a h is the
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* modulation index.
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*
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* The following phase responses can be generated:
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* - LREC: Rectangular phase response.
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* - LRC: Raised cosine phase response, looks like 1 - cos(x).
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* - LSRC: Spectral raised cosine. This requires a rolloff factor beta.
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* The phase response is the Fourier transform of raised cosine
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* function.
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* - TFM: Tamed frequency modulation. This scheme minimizes phase change for
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* rapidly varying input symbols.
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* - GAUSSIAN: A Gaussian phase response. For a modulation index h = 1/2, this
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* results in GMSK.
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*
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* A short description of all these phase responses can be found in [1].
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*
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* [1]: Anderson, Aulin and Sundberg; Digital Phase Modulation
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*/
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static
std::vector<float>
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phase_response(cpm_type type,
unsigned
samples_per_sym,
unsigned
L,
double
beta=0.3);
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};
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}
// namespace analog
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}
// namespace gr
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#endif
/* INCLUDED_ANALOG_CPM_H */
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gr-analog
include
analog
cpm.h
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