GNU Radio Manual and C++ API Reference 3.8.5.0
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single_pole_iir.h
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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 <gnuradio/gr_complex.h>
28#include <stdexcept>
29
30namespace gr {
31namespace filter {
32
33/*!
34 * \brief class template for single pole IIR filter
35 */
36template <class o_type, class i_type, class tap_type>
38{
39public:
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() { d_prev_output = 0; }
77
78 o_type prev_output() const { return d_prev_output; }
79
80protected:
81 tap_type d_alpha;
84};
85
86//
87// general case. We may want to specialize this
88//
89template <class o_type, class i_type, class tap_type>
91{
92 o_type output;
93
94 output = d_alpha * input + d_one_minus_alpha * d_prev_output;
95 d_prev_output = output;
96
97 return (o_type)output;
98}
99
100
101template <class o_type, class i_type, class tap_type>
103 const i_type input[],
104 unsigned long n)
105{
106 for (unsigned i = 0; i < n; i++)
107 output[i] = filter(input[i]);
108}
109
110
111//
112// Specialized case for gr_complex output and double taps
113// We need to have a gr_complexd type for the calculations and prev_output variable (in
114// stead of double)
115
116template <class i_type>
117class single_pole_iir<gr_complex, i_type, double>
118{
119public:
120 /*!
121 * \brief construct new single pole IIR with given alpha
122 *
123 * computes y(i) = (1-alpha) * y(i-1) + alpha * x(i)
124 */
125 single_pole_iir(double alpha = 1.0)
126 {
127 d_prev_output = 0;
128 set_taps(alpha);
129 }
130
131 /*!
132 * \brief compute a single output value.
133 * \returns the filtered input value.
134 */
135 gr_complex filter(const i_type input);
136
137 /*!
138 * \brief compute an array of N output values.
139 * \p input must have n valid entries.
140 */
141 void filterN(gr_complex output[], const i_type input[], unsigned long n);
142
143 /*!
144 * \brief install \p alpha as the current taps.
145 */
146 void set_taps(double alpha)
147 {
148 if (alpha < 0 || alpha > 1)
149 throw std::out_of_range("Alpha must be in [0, 1]\n");
150
151 d_alpha = alpha;
152 d_one_minus_alpha = 1.0 - alpha;
153 }
154
155 //! reset state to zero
156 void reset() { d_prev_output = 0; }
157
159
160protected:
161 double d_alpha;
164};
165
166template <class i_type>
168{
169 gr_complexd output;
170
171 output = d_alpha * (gr_complexd)input + d_one_minus_alpha * d_prev_output;
172 d_prev_output = output;
173
174 return (gr_complex)output;
175}
176
177// Do we need to specialize this, although it is the same as the general case?
178
179template <class i_type>
181 const i_type input[],
182 unsigned long n)
183{
184 for (unsigned i = 0; i < n; i++)
185 output[i] = filter(input[i]);
186}
187
188} /* namespace filter */
189} /* namespace gr */
190
191#endif /* INCLUDED_SINGLE_POLE_IIR_H */
gr_complexd prev_output() const
Definition single_pole_iir.h:158
double d_alpha
Definition single_pole_iir.h:161
void reset()
reset state to zero
Definition single_pole_iir.h:156
single_pole_iir(double alpha=1.0)
construct new single pole IIR with given alpha
Definition single_pole_iir.h:125
void set_taps(double alpha)
install alpha as the current taps.
Definition single_pole_iir.h:146
double d_one_minus_alpha
Definition single_pole_iir.h:162
gr_complexd d_prev_output
Definition single_pole_iir.h:163
class template for single pole IIR filter
Definition single_pole_iir.h:38
o_type prev_output() const
Definition single_pole_iir.h:78
single_pole_iir(tap_type alpha=1.0)
construct new single pole IIR with given alpha
Definition single_pole_iir.h:45
o_type filter(const i_type input)
compute a single output value.
Definition single_pole_iir.h:90
void reset()
reset state to zero
Definition single_pole_iir.h:76
tap_type d_one_minus_alpha
Definition single_pole_iir.h:82
tap_type d_alpha
Definition single_pole_iir.h:81
o_type d_prev_output
Definition single_pole_iir.h:83
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:102
void set_taps(tap_type alpha)
install alpha as the current taps.
Definition single_pole_iir.h:66
std::complex< double > gr_complexd
Definition gr_complex.h:28
std::complex< float > gr_complex
Definition gr_complex.h:27
GNU Radio logging wrapper for log4cpp library (C++ port of log4j)
Definition basic_block.h:46