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beginning of notch filter implementation

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AlexandreRouma 2021-12-08 11:59:04 +01:00
parent c1942ac51d
commit f8ff67c5b0
1 changed files with 135 additions and 68 deletions
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203
core/src/dsp/window.h
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@ -2,6 +2,7 @@
#include <dsp/block.h> #include <dsp/block.h>
#include <dsp/types.h> #include <dsp/types.h>
#include <dsp/utils/window_functions.h> #include <dsp/utils/window_functions.h>
#include <fftw3.h>
namespace dsp { namespace dsp {
namespace filter_window { namespace filter_window {
@ -187,86 +188,152 @@ namespace dsp {
} }
class RRCTaps : public filter_window::generic_window { class RRCTaps : public filter_window::generic_window {
public: public:
RRCTaps() {} RRCTaps() {}
RRCTaps(int tapCount, float sampleRate, float baudRate, float alpha) { init(tapCount, sampleRate, baudRate, alpha); } RRCTaps(int tapCount, float sampleRate, float baudRate, float alpha) { init(tapCount, sampleRate, baudRate, alpha); }
void init(int tapCount, float sampleRate, float baudRate, float alpha) { void init(int tapCount, float sampleRate, float baudRate, float alpha) {
_tapCount = tapCount; _tapCount = tapCount;
_sampleRate = sampleRate; _sampleRate = sampleRate;
_baudRate = baudRate; _baudRate = baudRate;
_alpha = alpha; _alpha = alpha;
} }
int getTapCount() { int getTapCount() {
return _tapCount; return _tapCount;
} }
void setSampleRate(float sampleRate) { void setSampleRate(float sampleRate) {
_sampleRate = sampleRate; _sampleRate = sampleRate;
} }
void setBaudRate(float baudRate) { void setBaudRate(float baudRate) {
_baudRate = baudRate; _baudRate = baudRate;
} }
void setTapCount(int count) { void setTapCount(int count) {
_tapCount = count; _tapCount = count;
} }
void setAlpha(float alpha) { void setAlpha(float alpha) {
_alpha = alpha; _alpha = alpha;
} }
void createTaps(float* taps, int tapCount, float factor = 1.0f) { void createTaps(float* taps, int tapCount, float factor = 1.0f) {
// ======== CREDIT: GNU Radio ========= // ======== CREDIT: GNU Radio =========
tapCount |= 1; // ensure that tapCount is odd tapCount |= 1; // ensure that tapCount is odd
double spb = _sampleRate / _baudRate; // samples per bit/symbol double spb = _sampleRate / _baudRate; // samples per bit/symbol
double scale = 0; double scale = 0;
for (int i = 0; i < tapCount; i++) for (int i = 0; i < tapCount; i++)
{ {
double x1, x2, x3, num, den; double x1, x2, x3, num, den;
double xindx = i - tapCount / 2; double xindx = i - tapCount / 2;
x1 = FL_M_PI * xindx / spb; x1 = FL_M_PI * xindx / spb;
x2 = 4 * _alpha * xindx / spb; x2 = 4 * _alpha * xindx / spb;
x3 = x2 * x2 - 1; x3 = x2 * x2 - 1;
// Avoid Rounding errors... // Avoid Rounding errors...
if (fabs(x3) >= 0.000001) { if (fabs(x3) >= 0.000001) {
if (i != tapCount / 2) if (i != tapCount / 2)
num = cos((1 + _alpha) * x1) + num = cos((1 + _alpha) * x1) +
sin((1 - _alpha) * x1) / (4 * _alpha * xindx / spb); sin((1 - _alpha) * x1) / (4 * _alpha * xindx / spb);
else else
num = cos((1 + _alpha) * x1) + (1 - _alpha) * FL_M_PI / (4 * _alpha); num = cos((1 + _alpha) * x1) + (1 - _alpha) * FL_M_PI / (4 * _alpha);
den = x3 * FL_M_PI; den = x3 * FL_M_PI;
}
else {
if (_alpha == 1)
{
taps[i] = -1;
scale += taps[i];
continue;
}
x3 = (1 - _alpha) * x1;
x2 = (1 + _alpha) * x1;
num = (sin(x2) * (1 + _alpha) * FL_M_PI -
cos(x3) * ((1 - _alpha) * FL_M_PI * spb) / (4 * _alpha * xindx) +
sin(x3) * spb * spb / (4 * _alpha * xindx * xindx));
den = -32 * FL_M_PI * _alpha * _alpha * xindx / spb;
}
taps[i] = 4 * _alpha * num / den;
scale += taps[i];
} }
else {
for (int i = 0; i < tapCount; i++) { if (_alpha == 1)
taps[i] = taps[i] / scale; {
taps[i] = -1;
scale += taps[i];
continue;
}
x3 = (1 - _alpha) * x1;
x2 = (1 + _alpha) * x1;
num = (sin(x2) * (1 + _alpha) * FL_M_PI -
cos(x3) * ((1 - _alpha) * FL_M_PI * spb) / (4 * _alpha * xindx) +
sin(x3) * spb * spb / (4 * _alpha * xindx * xindx));
den = -32 * FL_M_PI * _alpha * _alpha * xindx / spb;
} }
taps[i] = 4 * _alpha * num / den;
scale += taps[i];
} }
private: for (int i = 0; i < tapCount; i++) {
int _tapCount; taps[i] = taps[i] / scale;
float _sampleRate, _baudRate, _alpha; }
}
}; private:
int _tapCount;
float _sampleRate, _baudRate, _alpha;
};
class NotchWindow : public filter_window::generic_window {
public:
NotchWindow() {}
NotchWindow(float frequency, float width, float sampleRate, int tapCount) { init(frequency, width, sampleRate, tapCount); }
~NotchWindow() {
if (fft_in) { fftwf_free(fft_in); }
if (fft_out) { fftwf_free(fft_out); }
fftwf_destroy_plan(fft_plan);
}
void init(float frequency, float width, float sampleRate, int tapCount) {
_frequency = frequency;
_width = width;
_sampleRate = sampleRate;
_tapCount = _tapCount;
fft_in = (complex_t*)fftwf_malloc(_tapCount * sizeof(complex_t));
fft_out = (complex_t*)fftwf_malloc(_tapCount * sizeof(complex_t));
fft_plan = fftwf_plan_dft_1d(_tapCount, (fftwf_complex*)fft_in, (fftwf_complex*)fft_out, FFTW_BACKWARD, FFTW_ESTIMATE);
}
void setFrequency(float frequency) {
_frequency = frequency;
}
void setWidth(float width) {
_width = width;
}
void setSampleRate(float sampleRate) {
_sampleRate = sampleRate;
}
void setTapCount(int count) {
_tapCount = count;
if (fft_in) { fftwf_free(fft_in); }
if (fft_out) { fftwf_free(fft_out); }
fftwf_destroy_plan(fft_plan);
fft_in = (complex_t*)fftwf_malloc(_tapCount * sizeof(complex_t));
fft_out = (complex_t*)fftwf_malloc(_tapCount * sizeof(complex_t));
fft_plan = fftwf_plan_dft_1d(_tapCount, (fftwf_complex*)fft_in, (fftwf_complex*)fft_out, FFTW_BACKWARD, FFTW_ESTIMATE);
}
int getTapCount() {
return _tapCount;
}
void createTaps(float* taps, int tapCount, float factor = 1.0f) {
}
private:
complex_t* fft_in = NULL;
complex_t* fft_out = NULL;
float _frequency, _width, _sampleRate;
int _tapCount;
fftwf_plan fft_plan;
};
} }