noaa_hrpt_pll_cf.cc

/* -*- c++ -*- */
/*
 * Copyright 2009 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 <noaa_hrpt_pll_cf.h>
#include <gr_io_signature.h>
#include <gr_math.h>
#include <gr_sincos.h>

#define M_TWOPI (2*M_PI)

noaa_hrpt_pll_cf_sptr
noaa_make_hrpt_pll_cf(float alpha, float beta, float max_offset)
{
  return gnuradio::get_initial_sptr(new noaa_hrpt_pll_cf(alpha, beta, max_offset));
}

noaa_hrpt_pll_cf::noaa_hrpt_pll_cf(float alpha, float beta, float max_offset)
  : gr_sync_block("noaa_hrpt_pll_cf",
		  gr_make_io_signature(1, 1, sizeof(gr_complex)),
		  gr_make_io_signature(1, 1, sizeof(float))),
    d_alpha(alpha), d_beta(beta), d_max_offset(max_offset),
    d_phase(0.0), d_freq(0.0)
{
}

float
phase_wrap(float phase)
{
  while (phase < -M_PI)
    phase += M_TWOPI;
  while (phase > M_PI)
    phase -= M_TWOPI;

  return phase;
}

int
noaa_hrpt_pll_cf::work(int noutput_items,
		       gr_vector_const_void_star &input_items,
		       gr_vector_void_star &output_items)
{
  const gr_complex *in = (const gr_complex *) input_items[0];
  float *out = (float *) output_items[0];

  for (int i = 0; i < noutput_items; i++) {

    // Generate and mix out carrier
    float re, im;
    gr_sincosf(d_phase, &im, &re);
    out[i] = (in[i]*gr_complex(re, -im)).imag();

    // Adjust PLL phase/frequency
    float error = phase_wrap(gr_fast_atan2f(in[i].imag(), in[i].real()) - d_phase);
    d_freq  = gr_branchless_clip(d_freq + error*d_beta, d_max_offset);
    d_phase = phase_wrap(d_phase + error*d_alpha + d_freq);

  }

  return noutput_items;
}