GNU Radio C++ API
gr_iir_filter_ffd.h
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1 /* -*- c++ -*- */
2 /*
3  * Copyright 2004 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
9  * the Free Software Foundation; either version 3, or (at your option)
10  * any later version.
11  *
12  * GNU Radio is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15  * GNU General Public License for more details.
16  *
17  * You should have received a copy of the GNU General Public License
18  * along with GNU Radio; see the file COPYING. If not, write to
19  * the Free Software Foundation, Inc., 51 Franklin Street,
20  * Boston, MA 02110-1301, USA.
21  */
22 
23 #ifndef INCLUDED_GR_IIR_FILTER_FFD_H
24 #define INCLUDED_GR_IIR_FILTER_FFD_H
25 
26 #include <gr_core_api.h>
27 #include <gr_sync_block.h>
28 #include <gri_iir.h>
29 #include <stdexcept>
30 
31 class gr_iir_filter_ffd;
34 gr_make_iir_filter_ffd (const std::vector<double> &fftaps,
35  const std::vector<double> &fbtaps) throw (std::invalid_argument);
36 
37 /*!
38  * \brief IIR filter with float input, float output and double taps
39  * \ingroup filter_blk
40  *
41  * This filter uses the Direct Form I implementation, where
42  * \p fftaps contains the feed-forward taps, and \p fbtaps the feedback ones.
43  *
44  *
45  * The input and output satisfy a difference equation of the form
46 
47  \f[
48  y[n] - \sum_{k=1}^{M} a_k y[n-k] = \sum_{k=0}^{N} b_k x[n-k]
49  \f]
50 
51  * with the corresponding rational system function
52 
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 
57  * Note that some texts define the system function with a + in the denominator.
58  * If you're using that convention, you'll need to negate the feedback taps.
59  */
61 {
62  private:
64  gr_make_iir_filter_ffd (const std::vector<double> &fftaps,
65  const std::vector<double> &fbtaps) throw (std::invalid_argument);
66 
68  std::vector<double> d_new_fftaps;
69  std::vector<double> d_new_fbtaps;
70  bool d_updated;
71 
72  /*!
73  * Construct an IIR filter with the given taps
74  */
75  gr_iir_filter_ffd (const std::vector<double> &fftaps,
76  const std::vector<double> &fbtaps) throw (std::invalid_argument);
77 
78  public:
80 
81  void set_taps (const std::vector<double> &fftaps,
82  const std::vector<double> &fbtaps) throw (std::invalid_argument);
83 
84  int work (int noutput_items,
85  gr_vector_const_void_star &input_items,
86  gr_vector_void_star &output_items);
87 };
88 
89 #endif