iir_filter_ffd.h

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/* -*- c++ -*- */
/*
 * Copyright 2004,2012 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_IIR_FILTER_FFD_H
#define INCLUDED_IIR_FILTER_FFD_H

#include <filter/api.h>
#include <gr_sync_block.h>

namespace gr {
  namespace filter {
    
    /*!
     * \brief  IIR filter with float input, float output and double taps
     * \ingroup filter_blk
     *
     * \details
     * This filter uses the Direct Form I implementation, where
     * \p fftaps contains the feed-forward taps, and \p fbtaps the feedback ones.
     *
     *
     * The input and output satisfy a difference equation of the form
     \htmlonly
     \f{
     y[n] - \sum_{k=1}^{M} a_k y[n-k] = \sum_{k=0}^{N} b_k x[n-k]
     \f}
     \endhtmlonly

     \xmlonly
     y[n] - \sum_{k=1}^{M} a_k y[n-k] = \sum_{k=0}^{N} b_k x[n-k]
     \endxmlonly

     * with the corresponding rational system function
     \htmlonly
     \f{
     H(z) = \ frac{\sum_{k=0}^{M} b_k z^{-k}}{1 - \sum_{k=1}^{N} a_k z^{-k}}
     \f}
     \endhtmlonly

     \xmlonly
     H(z) = \ frac{\sum_{k=0}^{M} b_k z^{-k}}{1 - \sum_{k=1}^{N} a_k z^{-k}}
     \endxmlonly

     * Note that some texts define the system function with a + in the
     * denominator. If you're using that convention, you'll need to
     * negate the feedback taps.
     */
    class FILTER_API iir_filter_ffd : virtual public gr_sync_block
    {
    public:
      // gr::filter::iir_filter_ffd::sptr
      typedef boost::shared_ptr<iir_filter_ffd> sptr;

      static sptr make(const std::vector<double> &fftaps,
                       const std::vector<double> &fbtaps);

      virtual void set_taps(const std::vector<double> &fftaps,
                            const std::vector<double> &fbtaps) = 0;
    };

  } /* namespace filter */
} /* namespace gr */

#endif /* INCLUDED_IIR_FILTER_FFD_H */