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Proof-of-concept TDR measurements

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This commit is contained in:
Jan Käberich 2020-10-27 22:07:14 +01:00
parent d313988bfd
commit e68a9abffe
18 changed files with 1276 additions and 718 deletions
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89
Software/PC_Application/Traces/trace.cpp
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@ -1,9 +1,12 @@
#include "trace.h"
#include <math.h>
#include "fftcomplex.h"
using namespace std;
Trace::Trace(QString name, QColor color, LiveParameter live)
: _name(name),
: tdr_users(0),
_name(name),
_color(color),
_liveType(LivedataType::Overwrite),
_liveParam(live),
@ -64,6 +67,12 @@ void Trace::addData(Trace::Data d) {
}
emit dataAdded(this, d);
emit dataChanged();
if(lower == _data.begin()) {
// received the first point, which means the last sweep just finished
if(tdr_users) {
updateTimeDomainData();
}
}
}
void Trace::setName(QString name) {
@ -137,12 +146,79 @@ void Trace::removeMarker(TraceMarker *m)
markers.erase(m);
emit markerRemoved(m);
}
//#include <iostream>
//#include <chrono>
void Trace::updateTimeDomainData()
{
// using namespace std::chrono;
// auto starttime = duration_cast< milliseconds >(
// system_clock::now().time_since_epoch()
// ).count();
auto steps = size();
if(minFreq() * size() != maxFreq()) {
// data is not available with correct frequency spacing, calculate required steps
steps = maxFreq() / minFreq();
}
const double PI = 3.141592653589793238463;
// reserve vector for negative frequenies and DC as well
vector<complex<double>> frequencyDomain(2*steps + 1);
// copy frequencies, use the flipped conjugate for negative part
for(unsigned int i = 1;i<=steps;i++) {
auto S = getData(minFreq() * i);
constexpr double alpha0 = 0.54;
auto hamming = alpha0 - (1.0 - alpha0) * -cos(PI * i / steps);
S *= hamming;
frequencyDomain[2 * steps - i + 1] = conj(S);
frequencyDomain[i] = S;
}
// use simple extrapolation from lowest two points to extract DC value
auto abs_DC = 2.0 * abs(frequencyDomain[1]) - abs(frequencyDomain[2]);
auto phase_DC = 2.0 * arg(frequencyDomain[1]) - arg(frequencyDomain[2]);
frequencyDomain[0] = polar(abs_DC, phase_DC);
auto fft_bins = frequencyDomain.size();
timeDomain.clear();
timeDomain.resize(fft_bins);
const double fs = 1.0 / (minFreq() * fft_bins);
double last_step = 0.0;
Fft::transform(frequencyDomain, true);
for(unsigned int i = 0;i<fft_bins;i++) {
TimedomainData t;
t.time = fs * i;
t.impulseResponse = real(frequencyDomain[i]) / fft_bins;
t.stepResponse = last_step;
last_step += t.impulseResponse;
timeDomain.push_back(t);
}
// auto duration = duration_cast< milliseconds >(
// system_clock::now().time_since_epoch()
// ).count() - starttime;
// cout << "TDR: " << this << " (took " << duration << "ms)" <<endl;
}
void Trace::setReflection(bool value)
{
reflection = value;
}
void Trace::addTDRinterest()
{
if(tdr_users == 0) {
// no recent time domain data available, calculate now
updateTimeDomainData();
}
tdr_users++;
}
void Trace::removeTDRinterest()
{
if(tdr_users > 0) {
tdr_users--;
}
}
void Trace::setCalibration(bool value)
{
calibration = value;
@ -288,7 +364,16 @@ std::complex<double> Trace::getData(double frequency)
return std::numeric_limits<std::complex<double>>::quiet_NaN();
}
return sample(index(frequency)).S;
auto i = index(frequency);
if(_data.at(i).frequency == frequency) {
return _data[i].S;
} else {
// no exact frequency match, needs to interpolate
auto high = _data[i];
auto low = _data[i-1];
double alpha = (frequency - low.frequency) / (high.frequency - low.frequency);
return low.S * (1 - alpha) + high.S * alpha;
}
}
int Trace::index(double frequency)