-
Notifications
You must be signed in to change notification settings - Fork 6
/
Filter.h
172 lines (136 loc) · 4.28 KB
/
Filter.h
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
#ifndef SOFTFM_FILTER_H
#define SOFTFM_FILTER_H
#include <cassert>
#include <cmath>
#include <cstdint>
#include <algorithm>
#include <complex>
#include <vector>
#include "SdrberryTypeDefs.h"
#include "DataBuffer.h"
/** Fine tuner which shifts the frequency of an IQ signal by a fixed offset. */
class FineTuner
{
public:
/**
* Construct fine tuner.
*
* table_size :: Size of internal sin/cos tables, determines the resolution
* of the frequency shift.
*
* freq_shift :: Frequency shift. Signal frequency will be shifted by
* (sample_rate * freq_shift / table_size).
*/
FineTuner(unsigned int table_size, int freq_shift);
/** Process samples. */
void process(const IQSampleVector& samples_in, IQSampleVector& samples_out);
private:
unsigned int m_index;
IQSampleVector m_table;
};
/** Low-pass filter for IQ samples, based on Lanczos FIR filter. */
class LowPassFilterFirIQ
{
public:
/**
* Construct low-pass filter.
*
* filter_order :: FIR filter order.
* cutoff :: Cutoff frequency relative to the full sample rate
* (valid range 0.0 ... 0.5).
*/
LowPassFilterFirIQ(unsigned int filter_order, double cutoff);
/** Process samples. */
void process(const IQSampleVector& samples_in, IQSampleVector& samples_out);
private:
std::vector<IQSample::value_type> m_coeff;
IQSampleVector m_state;
};
/**
* Downsampler with low-pass FIR filter for real-valued signals.
*
* Step 1: Low-pass filter based on Lanczos FIR filter
* Step 2: (optional) Decimation by an arbitrary factor (integer or float)
*/
class DownsampleFilter
{
public:
/**
* Construct low-pass filter with optional downsampling.
*
* filter_order :: FIR filter order
* cutoff :: Cutoff frequency relative to the full input sample rate
* (valid range 0.0 .. 0.5)
* downsample :: Decimation factor (>= 1) or 1 to disable
* integer_factor :: Enables a faster and more precise algorithm that
* only works for integer downsample factors.
*
* The output sample rate is (input_sample_rate / downsample)
*/
DownsampleFilter(unsigned int filter_order, double cutoff,
double downsample=1, bool integer_factor=true);
/** Process samples. */
void process(const SampleVector& samples_in, SampleVector& samples_out);
private:
double m_downsample;
unsigned int m_downsample_int;
unsigned int m_pos_int;
Sample m_pos_frac;
SampleVector m_coeff;
SampleVector m_state;
};
/** First order low-pass IIR filter for real-valued signals. */
class LowPassFilterRC
{
public:
/**
* Construct 1st order low-pass IIR filter.
*
* timeconst :: RC time constant in seconds (1 / (2 * PI * cutoff_freq)
*/
LowPassFilterRC(double timeconst);
/** Process samples. */
void process(const SampleVector& samples_in, SampleVector& samples_out);
/** Process samples in-place. */
void process_inplace(SampleVector& samples);
private:
double m_timeconst;
Sample m_y1;
};
/** Low-pass filter for real-valued signals based on Butterworth IIR filter. */
class LowPassFilterIir
{
public:
/**
* Construct 4th order low-pass IIR filter.
*
* cutoff :: Low-pass cutoff relative to the sample frequency
* (valid range 0.0 .. 0.5, 0.5 = Nyquist)
*/
LowPassFilterIir(double cutoff);
/** Process samples. */
void process(const SampleVector& samples_in, SampleVector& samples_out);
private:
Sample b0, a1, a2, a3, a4;
Sample y1, y2, y3, y4;
};
/** High-pass filter for real-valued signals based on Butterworth IIR filter. */
class HighPassFilterIir
{
public:
/**
* Construct 2nd order high-pass IIR filter.
*
* cutoff :: High-pass cutoff relative to the sample frequency
* (valid range 0.0 .. 0.5, 0.5 = Nyquist)
*/
HighPassFilterIir(double cutoff);
/** Process samples. */
void process(const SampleVector& samples_in, SampleVector& samples_out);
/** Process samples in-place. */
void process_inplace(SampleVector& samples);
private:
Sample b0, b1, b2, a1, a2;
Sample x1, x2, y1, y2;
};
#endif