GNU Radio 3.6.2 C++ API
iir_filter_ffd.h
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1 /* -*- c++ -*- */
2 /*
3  * Copyright 2004,2012 Free Software Foundation, Inc.
4  *
5  * This file is part of GNU Radio
6  *
7  * GNU Radio is free software; you can redistribute it and/or modify
8  * it under the terms of the GNU General Public License as published by
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15  * GNU General Public License for more details.
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17  * You should have received a copy of the GNU General Public License
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19  * the Free Software Foundation, Inc., 51 Franklin Street,
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21  */
22 
23 #ifndef INCLUDED_IIR_FILTER_FFD_H
24 #define INCLUDED_IIR_FILTER_FFD_H
25 
26 #include <filter/api.h>
27 #include <gr_sync_block.h>
28 
29 namespace gr {
30  namespace filter {
31 
32  /*!
33  * \brief IIR filter with float input, float output and double taps
34  * \ingroup filter_blk
35  *
36  * This filter uses the Direct Form I implementation, where
37  * \p fftaps contains the feed-forward taps, and \p fbtaps the feedback ones.
38  *
39  *
40  * The input and output satisfy a difference equation of the form
41  \htmlonly
42  \f{
43  y[n] - \sum_{k=1}^{M} a_k y[n-k] = \sum_{k=0}^{N} b_k x[n-k]
44  \f}
45  \endhtmlonly
46 
47  \xmlonly
48  y[n] - \sum_{k=1}^{M} a_k y[n-k] = \sum_{k=0}^{N} b_k x[n-k]
49  \endxmlonly
50 
51  * with the corresponding rational system function
52  \htmlonly
53  \f{
54  H(z) = \ frac{\sum_{k=0}^{M} b_k z^{-k}}{1 - \sum_{k=1}^{N} a_k z^{-k}}
55  \f}
56  \endhtmlonly
57 
58  \xmlonly
59  H(z) = \ frac{\sum_{k=0}^{M} b_k z^{-k}}{1 - \sum_{k=1}^{N} a_k z^{-k}}
60  \endxmlonly
61 
62  * Note that some texts define the system function with a + in the
63  * denominator. If you're using that convention, you'll need to
64  * negate the feedback taps.
65  */
66  class FILTER_API iir_filter_ffd : virtual public gr_sync_block
67  {
68  public:
69  // gr::filter::iir_filter_ffd::sptr
71 
72  static sptr make(const std::vector<double> &fftaps,
73  const std::vector<double> &fbtaps);
74 
75  virtual void set_taps(const std::vector<double> &fftaps,
76  const std::vector<double> &fbtaps) = 0;
77  };
78 
79  } /* namespace filter */
80 } /* namespace gr */
81 
82 #endif /* INCLUDED_IIR_FILTER_FFD_H */