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 <gnuradio/filter/api.h>
#include <gnuradio/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.
 *
 * \p oldstyle: The old style of the IIR filter uses feedback
 * taps that are negative of what most definitions use (scipy
 * and Matlab among them). This parameter keeps using the old
 * GNU Radio style and is set to TRUE by default. When taps
 * generated from scipy, Matlab, or gr_filter_design, use the
 * new style by setting this to FALSE.
 *
 * The input and output satisfy a difference equation of the form
 \f[
   y[n] - \sum_{k=1}^{M} a_k y[n-k] = \sum_{k=0}^{N} b_k x[n-k]
 \f]
 
 \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
 \f[
 H(z) = \frac{\sum_{k=0}^{M} b_k z^{-k}}{1 - \sum_{k=1}^{N} a_k z^{-k}}
 \f]
 
 \xmlonly
 H(z) = \ frac{\sum_{k=0}^{M} b_k z^{-k}}{1 - \sum_{k=1}^{N} a_k z^{-k}}
 \endxmlonly
 
 */
class FILTER_API iir_filter_ffd : virtual public 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,
                     bool oldstyle = true);
 
    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 */