diff options
Diffstat (limited to 'gr-digital/lib/digital_clock_recovery_mm_cc.cc')
| -rw-r--r-- | gr-digital/lib/digital_clock_recovery_mm_cc.cc | 217 |
1 files changed, 217 insertions, 0 deletions
diff --git a/gr-digital/lib/digital_clock_recovery_mm_cc.cc b/gr-digital/lib/digital_clock_recovery_mm_cc.cc new file mode 100644 index 000000000..198eb4b89 --- /dev/null +++ b/gr-digital/lib/digital_clock_recovery_mm_cc.cc @@ -0,0 +1,217 @@ +/* -*- c++ -*- */ +/* + * Copyright 2005,2006,2010,2011 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. + */ + +#ifdef HAVE_CONFIG_H +#include "config.h" +#endif + +#include <gr_io_signature.h> +#include <gr_prefs.h> +#include <digital_clock_recovery_mm_cc.h> +#include <gri_mmse_fir_interpolator_cc.h> +#include <stdexcept> +#include <cstdio> + + +// Public constructor +static const int FUDGE = 16; + +digital_clock_recovery_mm_cc_sptr +digital_make_clock_recovery_mm_cc(float omega, float gain_omega, + float mu, float gain_mu, + float omega_relative_limit) +{ + return gnuradio::get_initial_sptr(new digital_clock_recovery_mm_cc (omega, + gain_omega, + mu, + gain_mu, + omega_relative_limit)); +} + +digital_clock_recovery_mm_cc::digital_clock_recovery_mm_cc (float omega, float gain_omega, + float mu, float gain_mu, + float omega_relative_limit) + : gr_block ("clock_recovery_mm_cc", + gr_make_io_signature (1, 1, sizeof (gr_complex)), + gr_make_io_signature2 (1, 2, sizeof (gr_complex), sizeof(float))), + d_mu (mu), d_omega(omega), d_gain_omega(gain_omega), + d_omega_relative_limit(omega_relative_limit), + d_gain_mu(gain_mu), d_last_sample(0), d_interp(new gri_mmse_fir_interpolator_cc()), + d_verbose(gr_prefs::singleton()->get_bool("clock_recovery_mm_cc", "verbose", false)), + d_p_2T(0), d_p_1T(0), d_p_0T(0), d_c_2T(0), d_c_1T(0), d_c_0T(0) +{ + if (omega <= 0.0) + throw std::out_of_range ("clock rate must be > 0"); + if (gain_mu < 0 || gain_omega < 0) + throw std::out_of_range ("Gains must be non-negative"); + + set_omega(omega); // also sets min and max omega + set_relative_rate (1.0 / omega); + set_history(3); // ensure 2 extra input sample is available +} + +digital_clock_recovery_mm_cc::~digital_clock_recovery_mm_cc () +{ + delete d_interp; +} + +void +digital_clock_recovery_mm_cc::forecast(int noutput_items, gr_vector_int &ninput_items_required) +{ + unsigned ninputs = ninput_items_required.size(); + for (unsigned i=0; i < ninputs; i++) + ninput_items_required[i] = + (int) ceil((noutput_items * d_omega) + d_interp->ntaps()) + FUDGE; +} + +gr_complex +digital_clock_recovery_mm_cc::slicer_0deg (gr_complex sample) +{ + float real=0, imag=0; + + if(sample.real() > 0) + real = 1; + if(sample.imag() > 0) + imag = 1; + return gr_complex(real,imag); +} + +gr_complex +digital_clock_recovery_mm_cc::slicer_45deg (gr_complex sample) +{ + float real= -1, imag = -1; + if(sample.real() > 0) + real=1; + if(sample.imag() > 0) + imag = 1; + return gr_complex(real,imag); +} + +/* + Modified Mueller and Muller clock recovery circuit + Based: + 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. +*/ + +int +digital_clock_recovery_mm_cc::general_work (int noutput_items, + gr_vector_int &ninput_items, + gr_vector_const_void_star &input_items, + gr_vector_void_star &output_items) +{ + const gr_complex *in = (const gr_complex *) input_items[0]; + gr_complex *out = (gr_complex *) output_items[0]; + float *foptr = (float *) output_items[1]; + + bool write_foptr = output_items.size() >= 2; + + int ii = 0; // input index + int oo = 0; // output index + int ni = ninput_items[0] - d_interp->ntaps() - FUDGE; // don't use more input than this + + assert(d_mu >= 0.0); + assert(d_mu <= 1.0); + + float mm_val=0; + gr_complex u, x, y; + + // This loop writes the error to the second output, if it exists + if (write_foptr) { + while(oo < noutput_items && ii < ni) { + d_p_2T = d_p_1T; + d_p_1T = d_p_0T; + d_p_0T = d_interp->interpolate (&in[ii], d_mu); + + d_c_2T = d_c_1T; + d_c_1T = d_c_0T; + d_c_0T = slicer_0deg(d_p_0T); + + x = (d_c_0T - d_c_2T) * conj(d_p_1T); + y = (d_p_0T - d_p_2T) * conj(d_c_1T); + u = y - x; + mm_val = u.real(); + out[oo++] = d_p_0T; + + // limit mm_val + mm_val = gr_branchless_clip(mm_val,4.0); + d_omega = d_omega + d_gain_omega * mm_val; + d_omega = d_omega_mid + gr_branchless_clip(d_omega-d_omega_mid, d_omega_relative_limit); // make sure we don't walk away + + d_mu = d_mu + d_omega + d_gain_mu * mm_val; + ii += (int)floor(d_mu); + d_mu -= floor(d_mu); + + // write the error signal to the second output + foptr[oo-1] = mm_val; + + if (ii < 0) // clamp it. This should only happen with bogus input + ii = 0; + } + } + // This loop does not write to the second output (ugly, but faster) + else { + while(oo < noutput_items && ii < ni) { + d_p_2T = d_p_1T; + d_p_1T = d_p_0T; + d_p_0T = d_interp->interpolate (&in[ii], d_mu); + + d_c_2T = d_c_1T; + d_c_1T = d_c_0T; + d_c_0T = slicer_0deg(d_p_0T); + + x = (d_c_0T - d_c_2T) * conj(d_p_1T); + y = (d_p_0T - d_p_2T) * conj(d_c_1T); + u = y - x; + mm_val = u.real(); + out[oo++] = d_p_0T; + + // limit mm_val + mm_val = gr_branchless_clip(mm_val,1.0); + + d_omega = d_omega + d_gain_omega * mm_val; + d_omega = d_omega_mid + gr_branchless_clip(d_omega-d_omega_mid, d_omega_relative_limit); // make sure we don't walk away + + d_mu = d_mu + d_omega + d_gain_mu * mm_val; + ii += (int)floor(d_mu); + d_mu -= floor(d_mu); + + if(d_verbose) { + printf("%f\t%f\n", d_omega, d_mu); + } + + if (ii < 0) // clamp it. This should only happen with bogus input + ii = 0; + } + } + + if (ii > 0){ + if (ii > ninput_items[0]){ + fprintf(stderr, "gr_clock_recovery_mm_cc: ii > ninput_items[0] (%d > %d)\n", + ii, ninput_items[0]); + assert(0); + } + consume_each (ii); + } + + return oo; +} |