gr_pfb_interpolator_ccf.h

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/* -*- 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.
 */


#ifndef INCLUDED_GR_PFB_INTERPOLATOR_CCF_H
#define INCLUDED_GR_PFB_INTERPOLATOR_CCF_H

#include <gr_sync_interpolator.h>

class gr_pfb_interpolator_ccf;
typedef boost::shared_ptr<gr_pfb_interpolator_ccf> gr_pfb_interpolator_ccf_sptr;
gr_pfb_interpolator_ccf_sptr gr_make_pfb_interpolator_ccf (unsigned int interp, 
                                                           const std::vector<float> &taps);

class gr_fir_ccf;

/*!
 * \class gr_pfb_interpolator_ccf
 * \brief Polyphase filterbank interpolator with gr_complex input,
 * gr_complex output and float taps
 *
 * \ingroup filter_blk
 * 
 * This block takes in a signal stream and performs interger up-
 * sampling (interpolation) with a polyphase filterbank. The first
 * input is the integer specifying how much to interpolate by. The
 * second input is a vector (Python list) of floating-point taps of
 * the prototype filter.
 *
 * The filter's taps should be based on the interpolation rate
 * specified. That is, the bandwidth specified is relative to the
 * bandwidth after interpolation.
 *
 * For example, using the GNU Radio's firdes utility to building
 * filters, we build a low-pass filter with a sampling rate of
 * <EM>fs</EM>, a 3-dB bandwidth of <EM>BW</EM> and a transition
 * bandwidth of <EM>TB</EM>. We can also specify the out-of-band
 * attenuation to use, ATT, and the filter window function (a
 * Blackman-harris window in this case). The first input is the gain,
 * which is also specified as the interpolation rate so that the
 * output levels are the same as the input (this creates an overall
 * increase in power).
 *
 *      <B><EM>self._taps = gr.firdes.low_pass_2(interp, interp*fs, BW, TB, 
 *           attenuation_dB=ATT, window=gr.firdes.WIN_BLACKMAN_hARRIS)</EM></B>
 *
 * The PFB interpolator code takes the taps generated above and builds
 * a set of filters. The set contains <EM>interp</EM> number of
 * filters and each filter contains ceil(taps.size()/interp) number of
 * taps. Each tap from the filter prototype is sequentially inserted
 * into the next filter. When all of the input taps are used, the
 * remaining filters in the filterbank are filled out with 0's to make
 * sure each filter has the same number of taps.
 *
 * The theory behind this block can be found in Chapter 7.1 of the
 * following book.
 *
 *    <B><EM>f. harris, "Multirate Signal Processing for Communication
 *       Systems</EM>," Upper Saddle River, NJ: Prentice Hall,
 *       Inc. 2004.</EM></B>
 */

class gr_pfb_interpolator_ccf : public gr_sync_interpolator
{
 private:
  /*!
   * Build the polyphase filterbank interpolator.
   * \param interp  (unsigned integer) Specifies the interpolation rate to use
   * \param taps    (vector/list of floats) The prototype filter to populate the filterbank. The taps
   *                                        should be generated at the interpolated sampling rate.
   */
  friend gr_pfb_interpolator_ccf_sptr gr_make_pfb_interpolator_ccf (unsigned int interp,
                                                                    const std::vector<float> &taps);

  std::vector<gr_fir_ccf*> d_filters;
  std::vector< std::vector<float> > d_taps;
  unsigned int             d_rate;
  unsigned int             d_taps_per_filter;
  bool                     d_updated;

  /*!
   * Construct a Polyphase filterbank interpolator
   * \param interp  (unsigned integer) Specifies the interpolation rate to use
   * \param taps    (vector/list of floats) The prototype filter to populate the filterbank. The taps
   *                                        should be generated at the interpolated sampling rate.
   */
  gr_pfb_interpolator_ccf (unsigned int interp, 
                           const std::vector<float> &taps);
  
public:
  ~gr_pfb_interpolator_ccf ();
  
  /*!
   * Resets the filterbank's filter taps with the new prototype filter
   * \param taps    (vector/list of floats) The prototype filter to populate the filterbank. The taps
   *                                        should be generated at the interpolated sampling rate.
   */
  void set_taps (const std::vector<float> &taps);

  /*!
   * Print all of the filterbank taps to screen.
   */
  void print_taps();
  
  int work (int noutput_items,
            gr_vector_const_void_star &input_items,
            gr_vector_void_star &output_items);
};

#endif