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Channel analyzer NG: autocorrelation corrections (2): corrected FFT aliasing
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@ -52,8 +52,7 @@ ChannelAnalyzerNG::ChannelAnalyzerNG(DeviceSourceAPI *deviceAPI) :
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m_inputFrequencyOffset = 0;
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SSBFilter = new fftfilt(m_settings.m_lowCutoff / m_inputSampleRate, m_settings.m_bandwidth / m_inputSampleRate, ssbFftLen);
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DSBFilter = new fftfilt(m_settings.m_bandwidth / m_inputSampleRate, 2*ssbFftLen);
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m_corr = new fftcorr(4*ssbFftLen);
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//m_pll.computeCoefficients(0.05f, 0.707f, 1000.0f); // bandwidth, damping factor, loop gain
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m_corr = new fftcorr(8*ssbFftLen); // 8k for 4k effective samples
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m_pll.computeCoefficients(0.002f, 0.5f, 10.0f); // bandwidth, damping factor, loop gain
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applyChannelSettings(m_inputSampleRate, m_inputFrequencyOffset, true);
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@ -43,7 +43,7 @@ void fftcorr::init_fft()
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outptr = 0;
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}
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fftcorr::fftcorr(int len) : flen(len)
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fftcorr::fftcorr(int len) : flen(len), flen2(len>>1)
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{
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init_fft();
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}
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@ -66,7 +66,7 @@ int fftcorr::run(const cmplx& inA, const cmplx* inB, cmplx **out)
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dataB[inptrB++] = *inB;
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}
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if (inptrA < flen) {
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if (inptrA < flen2) {
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return 0;
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}
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@ -83,6 +83,7 @@ int fftcorr::run(const cmplx& inA, const cmplx* inB, cmplx **out)
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}
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std::transform(dataA, dataA+flen, dataBj, dataP, [](const cmplx& a, const cmplx& b) -> cmplx { return a*b; });
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fftA->InverseComplexFFT(dataP);
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std::fill(dataA, dataA+flen, 0);
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@ -95,7 +96,7 @@ int fftcorr::run(const cmplx& inA, const cmplx* inB, cmplx **out)
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}
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*out = dataP;
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return flen;
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return flen2;
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}
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const fftcorr::cmplx& fftcorr::run(const cmplx& inA, const cmplx* inB)
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@ -41,6 +41,7 @@ public:
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private:
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void init_fft();
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int flen; //!< FFT length
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int flen2; //!< half FFT length
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g_fft<float> *fftA;
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g_fft<float> *fftB;
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cmplx *dataA; // from A input
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