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proper phase correction for Re/Im Fourier transform (MUSR-206)

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suter_a
2011-11-14 20:24:27 +00:00
parent a41c518ecc
commit a63ed33de7
2 changed files with 12 additions and 1 deletions
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12
src/classes/PFourier.cpp
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@ -36,6 +36,7 @@ using namespace std;
#include "TH1F.h"
#include "TF1.h"
#include "TAxis.h"
//#include "TFile.h"
@ -179,9 +180,18 @@ void PFourier::Transform(UInt_t apodizationTag)
fftw_execute(fFFTwPlan);
// correct the phase for tstart != 0.0
// find the first bin >= fStartTime
Double_t shiftTime = 0.0;
for (Int_t i=1; i<fData->GetXaxis()->GetNbins(); i++) {
if (fData->GetXaxis()->GetBinCenter(i) >= fStartTime) {
shiftTime = fData->GetXaxis()->GetBinCenter(i);
break;
}
}
Double_t phase, re, im;
for (UInt_t i=0; i<fNoOfBins; i++) {
phase = 2.0*PI/(fTimeResolution*fNoOfBins) * i * fStartTime;
phase = 2.0*PI/(fTimeResolution*fNoOfBins) * i * shiftTime;
re = fOut[i][0] * cos(phase) + fOut[i][1] * sin(phase);
im = -fOut[i][0] * sin(phase) + fOut[i][1] * cos(phase);
fOut[i][0] = re;