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Added a FFT based correlation class

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f4exb 2018-05-20 10:42:14 +02:00
parent 48cac5385b
commit d673278f86
3 changed files with 171 additions and 0 deletions
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2
sdrbase/CMakeLists.txt
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@ -28,6 +28,7 @@ set(sdrbase_SOURCES
dsp/dspengine.cpp
dsp/dspdevicesourceengine.cpp
dsp/dspdevicesinkengine.cpp
dsp/fftcorr.cpp
dsp/fftengine.cpp
dsp/fftfilt.cxx
dsp/fftwindow.cpp
@ -118,6 +119,7 @@ set(sdrbase_HEADERS
dsp/dspdevicesourceengine.h
dsp/dspdevicesinkengine.h
dsp/dsptypes.h
dsp/fftcorr.h
dsp/fftengine.h
dsp/fftfilt.h
dsp/fftwengine.h

112
sdrbase/dsp/fftcorr.cpp Normal file
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@ -0,0 +1,112 @@
///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2018 F4EXB //
// written by Edouard Griffiths //
// //
// FFT based cross correlation //
// //
// See: http://liquidsdr.org/blog/pll-howto/ //
// Fixed filter registers saturation //
// Added order for PSK locking. This brilliant idea actually comes from this //
// post: https://www.dsprelated.com/showthread/comp.dsp/36356-1.php //
// //
// This program is free software; you can redistribute it and/or modify //
// it under the terms of the GNU General Public License as published by //
// the Free Software Foundation as version 3 of the License, or //
// //
// This program is distributed in the hope that it will be useful, //
// but WITHOUT ANY WARRANTY; without even the implied warranty of //
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the //
// GNU General Public License V3 for more details. //
// //
// You should have received a copy of the GNU General Public License //
// along with this program. If not, see <http://www.gnu.org/licenses/>. //
///////////////////////////////////////////////////////////////////////////////////
#include <algorithm>
#include "fftcorr.h"
void fftcorr::init_fft()
{
flen2 = flen >> 1;
fftA = new g_fft<float>(flen);
fftB = new g_fft<float>(flen);
dataA = new cmplx[flen];
dataB = new cmplx[flen];
dataBj = new cmplx[flen];
dataP = new cmplx[flen];
output = new cmplx[flen2];
ovlbuf = new cmplx[flen2];
std::fill(dataA, dataA+flen, 0);
std::fill(dataB, dataB+flen, 0);
std::fill(output, output+flen2, 0);
std::fill(ovlbuf, ovlbuf+flen2, 0);
inptrA = 0;
inptrB = 0;
}
fftcorr::fftcorr(int len) : flen(len), flen2(len>>1)
{
init_fft();
}
fftcorr::~fftcorr()
{
delete fftA;
delete fftB;
delete[] dataA;
delete[] dataB;
delete[] dataBj;
delete[] dataP;
delete[] output;
delete[] ovlbuf;
}
int fftcorr::run(const cmplx& inA, const cmplx* inB, cmplx **out)
{
dataA[inptrA++] = inA;
if (inB) {
dataB[inptrB++] = *inB;
}
if (inptrA < flen2) {
return 0;
}
fftA->ComplexFFT(dataA);
if (inB) {
fftB->ComplexFFT(dataB);
}
if (inB) {
std::transform(dataB, dataB+flen, dataBj, [](const cmplx& c) -> cmplx { return std::conj(c); });
} else {
std::transform(dataA, dataA+flen, dataBj, [](const cmplx& c) -> cmplx { return std::conj(c); });
}
std::transform(dataA, dataA+flen, dataBj, dataP, [](const cmplx& a, const cmplx& b) -> cmplx { return a*b; });
fftA->InverseComplexFFT(dataP);
for (int i = 0; i < flen2; i++)
{
output[i] = ovlbuf[i] + dataP[i];
ovlbuf[i] = dataP[flen2 + i];
}
std::fill(dataA, dataA+flen, 0);
inptrA = 0;
if (inB)
{
std::fill(dataB, dataB+flen, 0);
inptrB = 0;
}
*out = output;
return flen2;
}

57
sdrbase/dsp/fftcorr.h Normal file
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@ -0,0 +1,57 @@
///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2018 F4EXB //
// written by Edouard Griffiths //
// //
// FFT based cross correlation //
// //
// See: http://liquidsdr.org/blog/pll-howto/ //
// Fixed filter registers saturation //
// Added order for PSK locking. This brilliant idea actually comes from this //
// post: https://www.dsprelated.com/showthread/comp.dsp/36356-1.php //
// //
// This program is free software; you can redistribute it and/or modify //
// it under the terms of the GNU General Public License as published by //
// the Free Software Foundation as version 3 of the License, or //
// //
// This program is distributed in the hope that it will be useful, //
// but WITHOUT ANY WARRANTY; without even the implied warranty of //
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the //
// GNU General Public License V3 for more details. //
// //
// You should have received a copy of the GNU General Public License //
// along with this program. If not, see <http://www.gnu.org/licenses/>. //
///////////////////////////////////////////////////////////////////////////////////
#ifndef SDRBASE_DSP_FFTCORR_H_
#define SDRBASE_DSP_FFTCORR_H_
#include <complex>
#include "gfft.h"
#include "export.h"
class SDRBASE_API fftcorr {
public:
typedef std::complex<float> cmplx;
fftcorr(int len);
~fftcorr();
int run(const cmplx& inA, const cmplx* inB, cmplx **out); //!< if inB = 0 then run auto-correlation
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
cmplx *dataB; // from B input
cmplx *dataBj; // conjugate of B
cmplx *dataP; // product of A with conjugate of B
cmplx *ovlbuf;
cmplx *output;
int inptrA;
int inptrB;
};
#endif /* SDRBASE_DSP_FFTCORR_H_ */