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sdrangel/sdrbase/dsp/fftcorr.cpp

112 lines
3.5 KiB
C++

///////////////////////////////////////////////////////////////////////////////////
// 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()
{
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];
std::fill(dataA, dataA+flen, 0);
std::fill(dataB, dataB+flen, 0);
inptrA = 0;
inptrB = 0;
outptr = 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;
}
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);
std::fill(dataA, dataA+flen, 0);
inptrA = 0;
if (inB)
{
std::fill(dataB, dataB+flen, 0);
inptrB = 0;
}
*out = dataP;
return flen2;
}
const fftcorr::cmplx& fftcorr::run(const cmplx& inA, const cmplx* inB)
{
cmplx *dummy;
if (run(inA, inB, &dummy)) {
outptr = 0;
}
return dataP[outptr++];
}