GNU Radio Manual and C++ API Reference  3.7.13.4
The Free & Open Software Radio Ecosystem
single_pole_iir.h
Go to the documentation of this file.
1 /* -*- c++ -*- */
2 /*
3  * Copyright 2002,2006,2012 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
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_SINGLE_POLE_IIR_H
24 #define INCLUDED_SINGLE_POLE_IIR_H
25 
26 #include <gnuradio/filter/api.h>
27 #include <stdexcept>
28 #include <gnuradio/gr_complex.h>
29 
30 namespace gr {
31  namespace filter {
32 
33  /*!
34  * \brief class template for single pole IIR filter
35  */
36  template<class o_type, class i_type, class tap_type>
38  {
39  public:
40  /*!
41  * \brief construct new single pole IIR with given alpha
42  *
43  * computes y(i) = (1-alpha) * y(i-1) + alpha * x(i)
44  */
45  single_pole_iir(tap_type alpha = 1.0)
46  {
47  d_prev_output = 0;
48  set_taps(alpha);
49  }
50 
51  /*!
52  * \brief compute a single output value.
53  * \returns the filtered input value.
54  */
55  o_type filter(const i_type input);
56 
57  /*!
58  * \brief compute an array of N output values.
59  * \p input must have n valid entries.
60  */
61  void filterN(o_type output[], const i_type input[], unsigned long n);
62 
63  /*!
64  * \brief install \p alpha as the current taps.
65  */
66  void set_taps(tap_type alpha)
67  {
68  if(alpha < 0 || alpha > 1)
69  throw std::out_of_range("Alpha must be in [0, 1]\n");
70 
71  d_alpha = alpha;
72  d_one_minus_alpha = 1.0 - alpha;
73  }
74 
75  //! reset state to zero
76  void reset()
77  {
78  d_prev_output = 0;
79  }
80 
81  o_type prev_output() const { return d_prev_output; }
82 
83  protected:
84  tap_type d_alpha;
86  o_type d_prev_output;
87  };
88 
89  //
90  // general case. We may want to specialize this
91  //
92  template<class o_type, class i_type, class tap_type>
93  o_type
95  {
96  o_type output;
97 
98  output = d_alpha * input + d_one_minus_alpha * d_prev_output;
99  d_prev_output = output;
100 
101  return (o_type) output;
102  }
103 
104 
105  template<class o_type, class i_type, class tap_type>
106  void
108  const i_type input[],
109  unsigned long n)
110  {
111  for(unsigned i = 0; i < n; i++)
112  output[i] = filter(input[i]);
113  }
114 
115 
116  //
117  // Specialized case for gr_complex output and double taps
118  // We need to have a gr_complexd type for the calculations and prev_output variable (in stead of double)
119 
120  template<class i_type>
121  class single_pole_iir<gr_complex, i_type, double>
122  {
123  public:
124  /*!
125  * \brief construct new single pole IIR with given alpha
126  *
127  * computes y(i) = (1-alpha) * y(i-1) + alpha * x(i)
128  */
129  single_pole_iir(double alpha = 1.0)
130  {
131  d_prev_output = 0;
132  set_taps(alpha);
133  }
134 
135  /*!
136  * \brief compute a single output value.
137  * \returns the filtered input value.
138  */
139  gr_complex filter(const i_type input);
140 
141  /*!
142  * \brief compute an array of N output values.
143  * \p input must have n valid entries.
144  */
145  void filterN(gr_complex output[], const i_type input[], unsigned long n);
146 
147  /*!
148  * \brief install \p alpha as the current taps.
149  */
150  void set_taps(double alpha)
151  {
152  if(alpha < 0 || alpha > 1)
153  throw std::out_of_range("Alpha must be in [0, 1]\n");
154 
155  d_alpha = alpha;
156  d_one_minus_alpha = 1.0 - alpha;
157  }
158 
159  //! reset state to zero
160  void reset()
161  {
162  d_prev_output = 0;
163  }
164 
166 
167  protected:
168  double d_alpha;
171  };
172 
173  template< class i_type>
174  gr_complex
176  {
177  gr_complexd output;
178 
179  output = d_alpha * (gr_complexd)input + d_one_minus_alpha * d_prev_output;
180  d_prev_output = output;
181 
182  return (gr_complex) output;
183  }
184 
185  //Do we need to specialize this, although it is the same as the general case?
186 
187  template<class i_type>
188  void
190  const i_type input[],
191  unsigned long n)
192  {
193  for(unsigned i = 0; i < n; i++)
194  output[i] = filter(input[i]);
195  }
196 
197  } /* namespace filter */
198 } /* namespace gr */
199 
200 #endif /* INCLUDED_SINGLE_POLE_IIR_H */
void reset()
reset state to zero
Definition: single_pole_iir.h:160
single_pole_iir(tap_type alpha=1.0)
construct new single pole IIR with given alpha
Definition: single_pole_iir.h:45
o_type prev_output() const
Definition: single_pole_iir.h:81
o_type d_prev_output
Definition: single_pole_iir.h:86
std::complex< double > gr_complexd
Definition: gr_complex.h:28
class template for single pole IIR filter
Definition: single_pole_iir.h:37
single_pole_iir(double alpha=1.0)
construct new single pole IIR with given alpha
Definition: single_pole_iir.h:129
std::complex< float > gr_complex
Definition: gr_complex.h:27
void set_taps(double alpha)
install alpha as the current taps.
Definition: single_pole_iir.h:150
Include this header to use the message passing features.
Definition: logger.h:695
gr_complexd d_prev_output
Definition: single_pole_iir.h:170
gr_complexd prev_output() const
Definition: single_pole_iir.h:165
void filterN(o_type output[], const i_type input[], unsigned long n)
compute an array of N output values. input must have n valid entries.
Definition: single_pole_iir.h:107
tap_type d_alpha
Definition: single_pole_iir.h:84
double d_one_minus_alpha
Definition: single_pole_iir.h:169
o_type filter(const i_type input)
compute a single output value.
Definition: single_pole_iir.h:94
tap_type d_one_minus_alpha
Definition: single_pole_iir.h:85
double d_alpha
Definition: single_pole_iir.h:168
void reset()
reset state to zero
Definition: single_pole_iir.h:76
void set_taps(tap_type alpha)
install alpha as the current taps.
Definition: single_pole_iir.h:66