kopia lustrzana https://github.com/vsamy/DiFipp
92 wiersze
2.3 KiB
C++
92 wiersze
2.3 KiB
C++
#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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m_poles.resize(order);
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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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T pi = static_cast<T>(M_PI);
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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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T scaleFactor = 2 * pi * fpw;
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auto thetaK = [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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// Compute poles
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std::complex<T> scalePole;
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for (size_t k = 1; k <= m_order; ++k) {
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scalePole = scaleFactor * std::complex<T>(-std::sin(thetaK(k)), std::cos(thetaK(k)));
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scalePole /= 2 * m_fs;
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m_poles[k - 1] = (T(1) + scalePole) / (T(1) - scalePole);
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}
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std::vector<std::complex<T>> numPoles(m_order, std::complex<T>(-1));
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std::vector<std::complex<T>> a = VietaAlgo<std::complex<T>>::polyCoeffFromRoot(m_poles);
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std::vector<std::complex<T>> b = VietaAlgo<std::complex<T>>::polyCoeffFromRoot(numPoles);
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T norm = 0;
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T sumB = 0;
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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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norm += m_aCoeff[i];
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sumB += m_bCoeff[i];
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}
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norm /= sumB;
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for (auto& b : m_bCoeff)
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b *= norm;
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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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} // namespace fratio
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