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https://github.com/jankae/LibreVNA.git
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optional 2xthru impedance correction
This commit is contained in:
Jan Käberich
parent
0f7c397a8a
commit
7352ad07b5
14 changed files with 1265 additions and 367 deletions
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@ -22,111 +22,11 @@ PortExtension::PortExtension()
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port2.delay = 0;
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port2.velocityFactor = 0.66;
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measuring = false;
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kit = nullptr;
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}
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void PortExtension::transformDatapoint(Protocol::Datapoint &d)
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{
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if(measuring) {
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if(measurements.size() > 0) {
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if(d.pointNum == 0) {
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// sweep complete, evaluate measurement
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double last_phase = 0.0;
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double phasediff_sum = 0.0;
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vector<double> att_x, att_y;
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double avg_x = 0.0, avg_y = 0.0;
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for(auto m : measurements) {
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// grab correct measurement
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complex<double> reflection;
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if(isPort1) {
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reflection = complex<double>(m.real_S11, m.imag_S11);
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} else {
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reflection = complex<double>(m.real_S22, m.imag_S22);
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}
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// remove calkit if specified
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if(!isIdeal) {
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complex<double> calStandard;
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auto standards = kit->toSOLT(m.frequency);
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if(isOpen) {
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calStandard = standards.Open;
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} else {
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calStandard = standards.Short;
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}
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// remove effect of calibration standard
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reflection /= calStandard;
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}
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// sum phase differences to previous point
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auto phase = arg(reflection);
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if(m.pointNum == 0) {
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last_phase = phase;
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} else {
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auto phasediff = phase - last_phase;
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last_phase = phase;
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if(phasediff > M_PI) {
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phasediff -= 2 * M_PI;
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} else if(phasediff <= -M_PI) {
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phasediff += 2 * M_PI;
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}
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phasediff_sum += phasediff;
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qDebug() << phasediff;
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}
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double x = sqrt(m.frequency / measurements.back().frequency);
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double y = 20*log10(abs(reflection));
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att_x.push_back(x);
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att_y.push_back(y);
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avg_x += x;
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avg_y += y;
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}
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auto phase = phasediff_sum / (measurements.size() - 1);
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auto freq_diff = measurements[1].frequency - measurements[0].frequency;
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auto delay = -phase / (2 * M_PI * freq_diff);
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// measured delay is two-way but port extension expects one-way
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delay /= 2;
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// calculate linear regression with transformed square root model
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avg_x /= measurements.size();
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avg_y /= measurements.size();
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double sum_top = 0.0;
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double sum_bottom = 0.0;
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for(unsigned int i=0;i<att_x.size();i++) {
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sum_top += (att_x[i] - avg_x)*(att_y[i] - avg_y);
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sum_bottom += (att_x[i] - avg_x)*(att_x[i] - avg_x);
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}
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double beta = sum_top / sum_bottom;
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double alpha = avg_y - beta * avg_x;
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double DCloss = -alpha / 2;
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double loss = -beta / 2;
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double freq = measurements.back().frequency;
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if(isPort1) {
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ui->P1Time->setValue(delay);
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ui->P1DCloss->setValue(DCloss);
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ui->P1Loss->setValue(loss);
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ui->P1Frequency->setValue(freq);
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} else {
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ui->P2Time->setValue(delay);
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ui->P2DCloss->setValue(DCloss);
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ui->P2Loss->setValue(loss);
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ui->P2Frequency->setValue(freq);
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}
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if(msgBox) {
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msgBox->close();
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msgBox = nullptr;
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}
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measurements.clear();
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} else {
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measurements.push_back(d);
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}
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} else if(d.pointNum == 0) {
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// first point of sweep, start measurement
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measurements.push_back(d);
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}
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}
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if(port1.enabled || port2.enabled) {
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// Convert measurements to complex variables
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auto S11 = complex<double>(d.real_S11, d.imag_S11);
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@ -299,16 +199,94 @@ void PortExtension::edit()
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dialog->show();
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}
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void PortExtension::measurementCompleted(std::vector<Protocol::Datapoint> m)
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{
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if(m.size() > 0) {
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double last_phase = 0.0;
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double phasediff_sum = 0.0;
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vector<double> att_x, att_y;
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double avg_x = 0.0, avg_y = 0.0;
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for(auto p : m) {
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// grab correct measurement
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complex<double> reflection;
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if(isPort1) {
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reflection = complex<double>(p.real_S11, p.imag_S11);
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} else {
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reflection = complex<double>(p.real_S22, p.imag_S22);
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}
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// remove calkit if specified
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if(!isIdeal) {
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complex<double> calStandard;
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auto standards = kit->toSOLT(p.frequency);
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if(isOpen) {
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calStandard = standards.Open;
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} else {
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calStandard = standards.Short;
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}
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// remove effect of calibration standard
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reflection /= calStandard;
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}
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// sum phase differences to previous point
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auto phase = arg(reflection);
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if(p.pointNum == 0) {
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last_phase = phase;
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} else {
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auto phasediff = phase - last_phase;
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last_phase = phase;
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if(phasediff > M_PI) {
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phasediff -= 2 * M_PI;
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} else if(phasediff <= -M_PI) {
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phasediff += 2 * M_PI;
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}
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phasediff_sum += phasediff;
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qDebug() << phasediff;
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}
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double x = sqrt(p.frequency / m.back().frequency);
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double y = 20*log10(abs(reflection));
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att_x.push_back(x);
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att_y.push_back(y);
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avg_x += x;
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avg_y += y;
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}
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auto phase = phasediff_sum / (m.size() - 1);
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auto freq_diff = m[1].frequency - m[0].frequency;
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auto delay = -phase / (2 * M_PI * freq_diff);
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// measured delay is two-way but port extension expects one-way
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delay /= 2;
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// calculate linear regression with transformed square root model
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avg_x /= m.size();
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avg_y /= m.size();
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double sum_top = 0.0;
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double sum_bottom = 0.0;
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for(unsigned int i=0;i<att_x.size();i++) {
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sum_top += (att_x[i] - avg_x)*(att_y[i] - avg_y);
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sum_bottom += (att_x[i] - avg_x)*(att_x[i] - avg_x);
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}
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double beta = sum_top / sum_bottom;
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double alpha = avg_y - beta * avg_x;
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double DCloss = -alpha / 2;
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double loss = -beta / 2;
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double freq = m.back().frequency;
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if(isPort1) {
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ui->P1Time->setValue(delay);
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ui->P1DCloss->setValue(DCloss);
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ui->P1Loss->setValue(loss);
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ui->P1Frequency->setValue(freq);
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} else {
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ui->P2Time->setValue(delay);
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ui->P2DCloss->setValue(DCloss);
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ui->P2Loss->setValue(loss);
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ui->P2Frequency->setValue(freq);
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}
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}
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}
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void PortExtension::startMeasurement()
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{
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measurements.clear();
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msgBox = new QMessageBox(QMessageBox::Information, "Auto port extension", "Taking measurement...", QMessageBox::Cancel);
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connect(msgBox, &QMessageBox::rejected, [=]() {
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measuring = false;
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measurements.clear();
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});
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msgBox->show();
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measuring = true;
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emit triggerMeasurement(isPort1, false, false, !isPort1);
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}
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void PortExtension::setCalkit(Calkit *kit)
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