GNU Radio 3.6.5.1 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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10  * any later version.
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14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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  * \details
37  * This filter uses the Direct Form I implementation, where
38  * \p fftaps contains the feed-forward taps, and \p fbtaps the feedback ones.
39  *
40  *
41  * The input and output satisfy a difference equation of the form
42  \htmlonly
43  \f{
44  y[n] - \sum_{k=1}^{M} a_k y[n-k] = \sum_{k=0}^{N} b_k x[n-k]
45  \f}
46  \endhtmlonly
47 
48  \xmlonly
49  y[n] - \sum_{k=1}^{M} a_k y[n-k] = \sum_{k=0}^{N} b_k x[n-k]
50  \endxmlonly
51 
52  * with the corresponding rational system function
53  \htmlonly
54  \f{
55  H(z) = \ frac{\sum_{k=0}^{M} b_k z^{-k}}{1 - \sum_{k=1}^{N} a_k z^{-k}}
56  \f}
57  \endhtmlonly
58 
59  \xmlonly
60  H(z) = \ frac{\sum_{k=0}^{M} b_k z^{-k}}{1 - \sum_{k=1}^{N} a_k z^{-k}}
61  \endxmlonly
62 
63  * Note that some texts define the system function with a + in the
64  * denominator. If you're using that convention, you'll need to
65  * negate the feedback taps.
66  */
67  class FILTER_API iir_filter_ffd : virtual public gr_sync_block
68  {
69  public:
70  // gr::filter::iir_filter_ffd::sptr
72 
73  static sptr make(const std::vector<double> &fftaps,
74  const std::vector<double> &fbtaps);
75 
76  virtual void set_taps(const std::vector<double> &fftaps,
77  const std::vector<double> &fbtaps) = 0;
78  };
79 
80  } /* namespace filter */
81 } /* namespace gr */
82 
83 #endif /* INCLUDED_IIR_FILTER_FFD_H */