gr_simple_squelch_cc.cc

这是用python语言写的一个数字广播的信号处理工具包。利用它

/* -*- c++ -*- */
/*
 * Copyright 2005 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_simple_squelch_cc.h>
#include <gr_io_signature.h>
#include <cmath>

gr_simple_squelch_cc_sptr
gr_make_simple_squelch_cc(double threshold_db, double alpha)
{
  return gr_simple_squelch_cc_sptr(new gr_simple_squelch_cc(threshold_db, alpha));
}

gr_simple_squelch_cc::gr_simple_squelch_cc (double threshold_db, double alpha)
  : gr_sync_block ("simple_squelch_cc",
		   gr_make_io_signature(1, 1, sizeof(gr_complex)),
		   gr_make_io_signature(1, 1, sizeof(gr_complex))),
    d_iir(alpha), d_unmuted(false)
{
  set_threshold (threshold_db);
}

gr_simple_squelch_cc::~gr_simple_squelch_cc()
{
}


int
gr_simple_squelch_cc::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];
  gr_complex *out = (gr_complex *) output_items[0];

  for (int i = 0; i < noutput_items; i++){
    double mag_sqrd = in[i].real()*in[i].real() + in[i].imag()*in[i].imag();
    double f = d_iir.filter(mag_sqrd);
    if (f >= d_threshold)
      out[i] = in[i];
    else
      out[i] = 0;
  }

  d_unmuted = d_iir.prev_output() >= d_threshold;
  return noutput_items;
}

void
gr_simple_squelch_cc::set_threshold(double decibels)
{
  // convert to absolute threshold (mag squared)
  d_threshold = std::pow(10.0, decibels/10);
}

double
gr_simple_squelch_cc::threshold() const
{
  return 10 * log10(d_threshold);
}

void
gr_simple_squelch_cc::set_alpha(double alpha)
{
  d_iir.set_taps(alpha);
}

std::vector<float>
gr_simple_squelch_cc::squelch_range() const
{
  std::vector<float> r(3);
  r[0] = -50.0;				// min	FIXME
  r[1] = +50.0;				// max	FIXME
  r[2] = (r[1] - r[0]) / 100;		// step size

  return r;
}