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Channel analyzer NG: autocorrelation corrections (2): corrected FFT aliasing

This commit is contained in:
f4exb 2018-05-20 20:23:41 +02:00
parent 8050266b28
commit f2f34ad9a9
3 changed files with 6 additions and 5 deletions
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3
plugins/channelrx/chanalyzerng/chanalyzerng.cpp
View File

@ -52,8 +52,7 @@ ChannelAnalyzerNG::ChannelAnalyzerNG(DeviceSourceAPI *deviceAPI) :
m_inputFrequencyOffset = 0;
SSBFilter = new fftfilt(m_settings.m_lowCutoff / m_inputSampleRate, m_settings.m_bandwidth / m_inputSampleRate, ssbFftLen);
DSBFilter = new fftfilt(m_settings.m_bandwidth / m_inputSampleRate, 2*ssbFftLen);
m_corr = new fftcorr(4*ssbFftLen);
//m_pll.computeCoefficients(0.05f, 0.707f, 1000.0f); // bandwidth, damping factor, loop gain
m_corr = new fftcorr(8*ssbFftLen); // 8k for 4k effective samples
m_pll.computeCoefficients(0.002f, 0.5f, 10.0f); // bandwidth, damping factor, loop gain
applyChannelSettings(m_inputSampleRate, m_inputFrequencyOffset, true);

7
sdrbase/dsp/fftcorr.cpp
View File

@ -43,7 +43,7 @@ void fftcorr::init_fft()
outptr = 0;
}
fftcorr::fftcorr(int len) : flen(len)
fftcorr::fftcorr(int len) : flen(len), flen2(len>>1)
{
init_fft();
}
@ -66,7 +66,7 @@ int fftcorr::run(const cmplx& inA, const cmplx* inB, cmplx **out)
dataB[inptrB++] = *inB;
}
if (inptrA < flen) {
if (inptrA < flen2) {
return 0;
}
@ -83,6 +83,7 @@ int fftcorr::run(const cmplx& inA, const cmplx* inB, cmplx **out)
}
std::transform(dataA, dataA+flen, dataBj, dataP, [](const cmplx& a, const cmplx& b) -> cmplx { return a*b; });
fftA->InverseComplexFFT(dataP);
std::fill(dataA, dataA+flen, 0);
@ -95,7 +96,7 @@ int fftcorr::run(const cmplx& inA, const cmplx* inB, cmplx **out)
}
*out = dataP;
return flen;
return flen2;
}
const fftcorr::cmplx& fftcorr::run(const cmplx& inA, const cmplx* inB)

1
sdrbase/dsp/fftcorr.h
View File

@ -41,6 +41,7 @@ public:
private:
void init_fft();
int flen; //!< FFT length
int flen2; //!< half FFT length
g_fft<float> *fftA;
g_fft<float> *fftB;
cmplx *dataA; // from A input