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/* -*- 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_signature (1, 2, sizeof (gr_complex))),
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];
gr_complex *foptr = (gr_complex *) 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,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);
// write the error signal to the second output
foptr[oo-1] = gr_complex(d_mu,0);
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;
}
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