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Diffstat (limited to 'gnuradio-core/src/lib/general/gr_cpm.h')
| -rw-r--r-- | gnuradio-core/src/lib/general/gr_cpm.h | 81 |
1 files changed, 81 insertions, 0 deletions
diff --git a/gnuradio-core/src/lib/general/gr_cpm.h b/gnuradio-core/src/lib/general/gr_cpm.h new file mode 100644 index 0000000000..f9b97f7ea7 --- /dev/null +++ b/gnuradio-core/src/lib/general/gr_cpm.h @@ -0,0 +1,81 @@ +/* -*- c++ -*- */ +/* + * Copyright 2010 Free Software Foundation, Inc. + * + * 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_GR_CPM_H +#define INCLUDED_GR_CPM_H + +#include <vector> + +#define M_TWOPI (2*M_PI) + +class gr_cpm +{ + public: + enum cpm_type { + LRC, + LSRC, + LREC, + TFM, + GAUSSIAN, + GENERIC = 999 + }; + + //! Return the taps for an interpolating FIR filter (gr_fir_filter_fff). + // + // These taps represent the phase response for use in a CPM modulator. + // + // Parameters: + // \p type: The CPM type (Rectangular, Raised Cosine, Spectral Raised Cosine, + // Tamed FM or Gaussian). + // \p samples_per_sym: Samples per symbol. + // \p L: The length of the phase response in symbols. + // \p beta: For Spectral Raised Cosine, this is the rolloff factor. For Gaussian + // phase responses, this the 3dB-time-bandwidth product. For all other + // cases, it is ignored. + // + // Output: returns a vector of length \p L * \p samples_per_sym. This can be used + // directly in an interpolating FIR filter such as gr_interp_fir_filter_fff + // with interpolation factor \p samples_per_sym. + // + // All taps are normalised s.t. \sum taps = 1; this causes a maximum phase change + // of h*pi between two symbols, where h is the modulation index. + // + // The following phase responses can be generated: + // * LREC: Rectangular phase response. + // * LRC: Raised cosine phase response, looks like 1 - cos(x). + // * LSRC: Spectral raised cosine. This requires a rolloff factor beta. + // The phase response is the Fourier transform of raised cosine + // function. + // * TFM: Tamed frequency modulation. This scheme minimizes phase change for + // rapidly varying input symbols. + // * GAUSSIAN: A Gaussian phase response. For a modulation index h = 1/2, this + // results in GMSK. + // + // A short description of all these phase responses can be found in [1]. + // + // + // [1]: Anderson, Aulin and Sundberg; Digital Phase Modulation + static std::vector<float> + phase_response(cpm_type type, unsigned samples_per_sym, unsigned L, double beta=0.3); +}; + +#endif /* INCLUDED_GR_CPM_H */ + |