GNU Radio 3.5.3.2 C++ API
gr_iir_filter_ffd.h
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00001 /* -*- c++ -*- */
00002 /*
00003  * Copyright 2004 Free Software Foundation, Inc.
00004  * 
00005  * This file is part of GNU Radio
00006  * 
00007  * GNU Radio is free software; you can redistribute it and/or modify
00008  * it under the terms of the GNU General Public License as published by
00009  * the Free Software Foundation; either version 3, or (at your option)
00010  * any later version.
00011  * 
00012  * GNU Radio is distributed in the hope that it will be useful,
00013  * but WITHOUT ANY WARRANTY; without even the implied warranty of
00014  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
00015  * GNU General Public License for more details.
00016  * 
00017  * You should have received a copy of the GNU General Public License
00018  * along with GNU Radio; see the file COPYING.  If not, write to
00019  * the Free Software Foundation, Inc., 51 Franklin Street,
00020  * Boston, MA 02110-1301, USA.
00021  */
00022 
00023 #ifndef INCLUDED_GR_IIR_FILTER_FFD_H
00024 #define INCLUDED_GR_IIR_FILTER_FFD_H
00025 
00026 #include <gr_core_api.h>
00027 #include <gr_sync_block.h>
00028 #include <gri_iir.h>
00029 #include <stdexcept>
00030 
00031 class gr_iir_filter_ffd;
00032 typedef boost::shared_ptr<gr_iir_filter_ffd> gr_iir_filter_ffd_sptr;
00033 GR_CORE_API gr_iir_filter_ffd_sptr 
00034 gr_make_iir_filter_ffd (const std::vector<double> &fftaps,
00035                         const std::vector<double> &fbtaps) throw (std::invalid_argument);
00036 
00037 /*!
00038  * \brief  IIR filter with float input, float output and double taps
00039  * \ingroup filter_blk
00040  *
00041  * This filter uses the Direct Form I implementation, where
00042  * \p fftaps contains the feed-forward taps, and \p fbtaps the feedback ones.
00043  *
00044  * 
00045  * The input and output satisfy a difference equation of the form
00046  \htmlonly
00047  \f{
00048  y[n] - \sum_{k=1}^{M} a_k y[n-k] = \sum_{k=0}^{N} b_k x[n-k]
00049  \f}
00050  \endhtmlonly
00051 
00052  \xmlonly
00053  y[n] - \sum_{k=1}^{M} a_k y[n-k] = \sum_{k=0}^{N} b_k x[n-k]
00054  \endxmlonly
00055 
00056  * with the corresponding rational system function
00057  \htmlonly
00058  \f{
00059  H(z) = \ frac{\sum_{k=0}^{M} b_k z^{-k}}{1 - \sum_{k=1}^{N} a_k z^{-k}}
00060  \f}
00061  \endhtmlonly
00062 
00063  \xmlonly
00064  H(z) = \ frac{\sum_{k=0}^{M} b_k z^{-k}}{1 - \sum_{k=1}^{N} a_k z^{-k}}
00065  \endxmlonly
00066 
00067  * Note that some texts define the system function with a + in the denominator.
00068  * If you're using that convention, you'll need to negate the feedback taps.
00069  */
00070 class GR_CORE_API gr_iir_filter_ffd : public gr_sync_block
00071 {
00072  private:
00073   friend GR_CORE_API gr_iir_filter_ffd_sptr 
00074   gr_make_iir_filter_ffd (const std::vector<double> &fftaps,
00075                           const std::vector<double> &fbtaps) throw (std::invalid_argument);
00076 
00077   gri_iir<float,float,double>           d_iir;
00078   std::vector<double>                   d_new_fftaps;
00079   std::vector<double>                   d_new_fbtaps;
00080   bool                                  d_updated;
00081 
00082   /*!
00083    * Construct an IIR filter with the given taps
00084    */
00085   gr_iir_filter_ffd (const std::vector<double> &fftaps,
00086                      const std::vector<double> &fbtaps) throw (std::invalid_argument);
00087 
00088  public:
00089   ~gr_iir_filter_ffd ();
00090 
00091   void set_taps (const std::vector<double> &fftaps,
00092                  const std::vector<double> &fbtaps) throw (std::invalid_argument);
00093 
00094   int work (int noutput_items,
00095             gr_vector_const_void_star &input_items,
00096             gr_vector_void_star &output_items);
00097 };
00098 
00099 #endif