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Diffstat (limited to 'gnuradio-core/src/lib/hier/gr_cpm.cc')
| -rw-r--r-- | gnuradio-core/src/lib/hier/gr_cpm.cc | 210 |
1 files changed, 0 insertions, 210 deletions
diff --git a/gnuradio-core/src/lib/hier/gr_cpm.cc b/gnuradio-core/src/lib/hier/gr_cpm.cc deleted file mode 100644 index 5eda182b2..000000000 --- a/gnuradio-core/src/lib/hier/gr_cpm.cc +++ /dev/null @@ -1,210 +0,0 @@ -/* -*- 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. - */ - -// Calculate the taps for the CPM phase responses - -#ifdef HAVE_CONFIG_H -#include "config.h" -#endif - -#include <cmath> -#include <cfloat> -#include <gr_cpm.h> - - -//! Normalised sinc function, sinc(x)=sin(pi*x)/pi*x -inline double -sinc(double x) -{ - if (x == 0) { - return 1.0; - } - - return sin(M_PI * x) / (M_PI * x); -} - - -//! Taps for L-RC CPM (Raised cosine of length L symbols) -std::vector<float> -generate_cpm_lrc_taps(unsigned samples_per_sym, unsigned L) -{ - std::vector<float> taps(samples_per_sym * L, 1.0/L/samples_per_sym); - for (int i = 0; i < samples_per_sym * L; i++) { - taps[i] *= 1 - cos(M_TWOPI * i / L / samples_per_sym); - } - - return taps; -} - - -/*! Taps for L-SRC CPM (Spectral raised cosine of length L symbols). - * - * L-SRC has a time-continuous phase response function of - * - * g(t) = 1/LT * sinc(2t/LT) * cos(beta * 2pi t / LT) / (1 - (4beta / LT * t)^2) - * - * which is the Fourier transform of a cos-rolloff function with rolloff - * beta, and looks like a sinc-function, multiplied with a rolloff term. - * We return the main lobe of the sinc, i.e., everything between the - * zero crossings. - * The time-discrete IR is thus - * - * g(k) = 1/Ls * sinc(2k/Ls) * cos(beta * pi k / Ls) / (1 - (4beta / Ls * k)^2) - * where k = 0...Ls-1 - * and s = samples per symbol. - */ -std::vector<float> -generate_cpm_lsrc_taps(unsigned samples_per_sym, unsigned L, double beta) -{ - double Ls = (double) L * samples_per_sym; - std::vector<double> taps_d(Ls, 0.0); - std::vector<float> taps(Ls, 0.0); - - for (int i = 0; i < samples_per_sym * L; i++) { - double k = i - Ls/2; // Causal to acausal - - taps_d[i] = 1.0 / Ls * sinc(2.0 * k / Ls); - - // For k = +/-Ls/4*beta, the rolloff term's cos-function becomes zero - // and the whole thing converges to PI/4 (to prove this, use de - // l'hopital's rule). - if (fabs(abs(k) - Ls/4/beta) < 2*DBL_EPSILON) { - taps_d[i] *= M_PI_4; - } else { - double tmp = 4.0 * beta * k / Ls; - taps_d[i] *= cos(beta * M_TWOPI * k / Ls) / (1 - tmp * tmp); - } - sum += taps_d[i]; - } - for (int i = 0; i < samples_per_sym * L; i++) { - taps[i] = (float) taps_d[i] / sum; - } - - return taps; -} - - -//! Taps for L-REC CPM (Rectangular pulse shape of length L symbols) -std::vector<float> -generate_cpm_lrec_taps(unsigned samples_per_sym, unsigned L) -{ - return std::vector<float>(samples_per_sym * L, 1.0/L/samples_per_sym); -} - - -//! Helper function for TFM -double tfm_g0(double k, double sps) -{ - if (k < 2 * DBL_EPSILON) { - return 1.145393004159143; // 1 + pi^2/48 / sqrt(2) - } - - const double pi2_24 = 0.411233516712057; // pi^2/24 - double f = M_PI * k / sps; - return sinc(k/sps) - pi2_24 * (2 * sin(f) - 2*f*cos(f) - f*f*sin(f)) / (f*f*f); -} - - -//! Taps for TFM CPM (Tamed frequency modulation) -// -// See [2, Chapter 2.7.2]. -// -// [2]: Anderson, Aulin and Sundberg; Digital Phase Modulation -std::vector<float> -generate_cpm_tfm_taps(unsigned sps, unsigned L) -{ - double causal_shift = (double) L * sps / 2; - std::vector<double> taps_d(Ls, 0.0); - std::vector<float> taps(Ls, 0.0); - - double sum = 0; - for (int i = 0; i < sps * L; i++) { - double k = (double)i - causal_shift; // Causal to acausal - - taps_d[i] = tfm_g0(k - sps, sps) + - 2 * tfm_g0(k, sps) + - tfm_g0(k + sps, sps); - sum += taps_d[i]; - } - for (int i = 0; i < samples_per_sym * L; i++) { - taps[i] = (float) taps_d[i] / sum; - } - - return taps; -} - - -//! Taps for Gaussian CPM. Phase response is truncated after \p L symbols. -// \p bt sets the 3dB-time-bandwidth product. -// -// Note: for h = 0.5, this is the phase response for GMSK. -// -// This C99-compatible formula for the taps is taken straight -// from [1, Chapter 9.2.3]. -// A version in Q-notation can be found in [2, Chapter 2.7.2]. -// -// [1]: Karl-Dirk Kammeyer; Nachrichtenübertragung, 4th Edition. -// [2]: Anderson, Aulin and Sundberg; Digital Phase Modulation -// -std::vector<float> -generate_cpm_gaussian_taps(unsigned samples_per_sym, unsigned L, double bt) -{ - double Ls = (double) L * samples_per_sym; - std::vector<double> taps_d(Ls, 0.0); - std::vector<float> taps(Ls, 0.0); - - // alpha = sqrt(2/ln(2)) * pi * BT - double alpha = 5.336446256636997 * bt; - for (int i = 0; i < samples_per_sym * L; i++) { - double k = i - Ls/2; // Causal to acausal - taps_d[i] = (erf(alpha * (k / samples_per_sym + 0.5)) - - erf(alpha * (k / samples_per_sym - 0.5))) - * 0.5 / samples_per_sym; - taps[i] = (float) taps_d[i]; - } - - return taps; -} - - -std::vector<float> -gr_cpm::phase_response(cpm_type type, unsigned samples_per_sym, unsigned L, double beta) -{ - switch (type) { - case LRC: - return generate_cpm_lrc_taps(samples_per_sym, L); - - case LSRC: - return generate_cpm_lsrc_taps(samples_per_sym, L, beta); - - case LREC: - return generate_cpm_lrec_taps(samples_per_sym, L); - - case TFM: - return generate_cpm_tfm_taps(samples_per_sym, L); - - case GAUSSIAN: - return generate_cpm_gaussian_taps(samples_per_sym, L, beta); - - default: - return generate_cpm_lrec_taps(samples_per_sym, 1); - } -} - |