GNU Radio 3.5.3.1 C++ API
gr_single_pole_iir_filter_ff.h
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1 /* -*- c++ -*- */
2 /*
3  * Copyright 2004,2005 Free Software Foundation, Inc.
4  *
5  * This file is part of GNU Radio
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7  * GNU Radio is free software; you can redistribute it and/or modify
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10  * any later version.
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15  * GNU General Public License for more details.
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21  */
22 
23 #ifndef INCLUDED_GR_SINGLE_POLE_IIR_FILTER_FF_H
24 #define INCLUDED_GR_SINGLE_POLE_IIR_FILTER_FF_H
25 
26 #include <gr_core_api.h>
27 #include <gr_sync_block.h>
28 #include <gr_single_pole_iir.h>
29 #include <stdexcept>
30 
33 
35 gr_make_single_pole_iir_filter_ff (double alpha, unsigned int vlen=1);
36 
37 /*!
38  * \brief single pole IIR filter with float input, float output
39  * \ingroup filter_blk
40  *
41  * The input and output satisfy a difference equation of the form
42  \htmlonly
43  \f{
44  y[n] - (1-alpha) y[n-1] = alpha x[n]
45  \f}
46  \endhtmlonly
47 
48  \xmlonly
49  y[n] - (1-alpha) y[n-1] = alpha x[n]
50  \endxmlonly
51 
52  * with the corresponding rational system function
53  \htmlonly
54  \f{
55  H(z) = \frac{alpha}{1 - (1-alpha) z^{-1}}
56  \f}
57  \endhtmlonly
58 
59  \xmlonly
60 H(z) = \ frac{alpha}{1 - (1-alpha) z^{-1}}
61  \endxmlonly
62 
63  * Note that some texts define the system function with a + in the denominator.
64  * If you're using that convention, you'll need to negate the feedback tap.
65  */
67 {
68  private:
70  gr_make_single_pole_iir_filter_ff (double alpha, unsigned int vlen);
71 
72  unsigned int d_vlen;
73  std::vector<gr_single_pole_iir<float,float,double> > d_iir;
74 
75  gr_single_pole_iir_filter_ff (double alpha, unsigned int vlen);
76 
77  public:
79 
80  void set_taps (double alpha);
81 
82  int work (int noutput_items,
83  gr_vector_const_void_star &input_items,
84  gr_vector_void_star &output_items);
85 };
86 
87 #endif