kopia lustrzana https://github.com/vsamy/DiFipp
145 wiersze
3.4 KiB
C++
145 wiersze
3.4 KiB
C++
#include "BilinearTransform.h"
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#include "polynome_functions.h"
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#include <cmath>
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#include <sstream>
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namespace fratio {
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template <typename T>
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Butterworth<T>::Butterworth(Type type)
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: m_type(type)
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{
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}
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template <typename T>
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Butterworth<T>::Butterworth(size_t order, T fc, T fs, Type type)
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: m_type(type)
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{
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initialize(order, fc, fs);
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}
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template <typename T>
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void Butterworth<T>::setFilterParameters(size_t order, T fc, T fs)
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{
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initialize(order, fc, fs);
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}
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template <typename T>
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void Butterworth<T>::initialize(size_t order, T fc, T fs)
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{
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if (m_fc > m_fs / 2.) {
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std::stringstream ss;
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ss << "The cut-off-frequency must be inferior to the sampling frequency"
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<< "\n Given cut-off-frequency is " << m_fc
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<< "\n Given sample frequency is " << m_fs;
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throw std::runtime_error(ss.str());
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}
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m_order = order;
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m_fc = fc;
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m_fs = fs;
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updateCoeffSize();
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computeDigitalRep();
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}
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template <typename T>
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void Butterworth<T>::computeDigitalRep()
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{
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// Continuous pre-warped frequency
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T fpw = (m_fs / PI) * std::tan(PI * m_fc / m_fs);
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// Compute poles
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std::complex<T> analogPole;
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std::vector<std::complex<T>> poles(m_order);
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for (size_t k = 1; k <= m_order; ++k) {
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analogPole = generateAnalogPole(fpw, k);
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BilinearTransform<std::complex<T>>::SToZ(m_fs, analogPole, poles[k - 1]);
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}
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std::vector<std::complex<T>> zeros = generateAnalogZeros();
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std::vector<std::complex<T>> a = VietaAlgo<std::complex<T>>::polyCoeffFromRoot(poles);
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std::vector<std::complex<T>> b = VietaAlgo<std::complex<T>>::polyCoeffFromRoot(zeros);
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for (size_t i = 0; i < m_order + 1; ++i) {
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m_aCoeff[i] = a[i].real();
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m_bCoeff[i] = b[i].real();
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}
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scaleAmplitude();
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checkCoeff(m_aCoeff, m_bCoeff);
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}
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template <typename T>
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void Butterworth<T>::updateCoeffSize()
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{
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m_aCoeff.resize(m_order + 1);
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m_bCoeff.resize(m_order + 1);
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resetFilter();
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}
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template <typename T>
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std::complex<T> Butterworth<T>::generateAnalogPole(T fpw, size_t k)
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{
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T scaleFactor = 2 * PI * fpw;
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auto thetaK = [pi = PI, order = m_order](size_t k) -> T {
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return (2 * k - 1) * pi / (2 * order);
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};
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std::complex<T> analogPole(-std::sin(thetaK(k)), std::cos(thetaK(k)));
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switch (m_type) {
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case Type::HighPass:
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return scaleFactor / analogPole;
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case Type::LowPass:
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default:
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return scaleFactor * analogPole;
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}
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}
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template <typename T>
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std::vector<std::complex<T>> Butterworth<T>::generateAnalogZeros()
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{
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switch (m_type) {
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case Type::HighPass:
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return std::vector<std::complex<T>>(m_order, std::complex<T>(1));
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case Type::LowPass:
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default:
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return std::vector<std::complex<T>>(m_order, std::complex<T>(-1));
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}
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}
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template <typename T>
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void Butterworth<T>::scaleAmplitude()
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{
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T scale = 0;
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T sumB = 0;
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switch (m_type) {
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case Type::HighPass:
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for (size_t i = 0; i < m_order + 1; ++i) {
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if (i % 2 == 0) {
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scale += m_aCoeff[i];
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sumB += m_bCoeff[i];
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} else {
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scale -= m_aCoeff[i];
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sumB -= m_bCoeff[i];
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}
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}
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break;
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case Type::LowPass:
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default:
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for (size_t i = 0; i < m_order + 1; ++i) {
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scale += m_aCoeff[i];
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sumB += m_bCoeff[i];
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}
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break;
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}
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scale /= sumB;
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for (auto& b : m_bCoeff)
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b *= scale;
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}
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} // namespace fratio
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