LibreVNA/Software/PC_Application/VNA/Deembedding/twothru.cpp

318 lines
12 KiB
C++

#include "twothru.h"
#include "CustomWidgets/informationbox.h"
#include "ui_twothrudialog.h"
#include "Traces/fftcomplex.h"
using namespace std;
TwoThru::TwoThru()
{
measuring = false;
}
void TwoThru::transformDatapoint(Protocol::Datapoint &p)
{
auto S11 = complex<double>(p.real_S11, p.imag_S11);
auto S12 = complex<double>(p.real_S12, p.imag_S12);
auto S21 = complex<double>(p.real_S21, p.imag_S21);
auto S22 = complex<double>(p.real_S22, p.imag_S22);
Sparam S(S11, S12, S21, S22);
Tparam meas(S);
if(measuring) {
if(measurements.size() > 0 && p.pointNum == 0) {
// complete sweep measured, exit measurement mode
measuring = false;
// calculate error boxes, see https://www.freelists.org/post/si-list/IEEE-P370-Opensource-Deembedding-MATLAB-functions
// create vectors of S parameters
vector<complex<double>> S11, S12, S21, S22;
vector<double> f;
for(auto m : measurements) {
if(m.frequency == 0) {
// ignore possible DC point
continue;
}
S11.push_back(complex<double>(m.real_S11, m.imag_S11));
S12.push_back(complex<double>(m.real_S12, m.imag_S12));
S21.push_back(complex<double>(m.real_S21, m.imag_S21));
S22.push_back(complex<double>(m.real_S22, m.imag_S22));
f.push_back(m.frequency);
}
auto n = f.size();
auto makeSymmetric = [](const vector<complex<double>> &in) -> vector<complex<double>> {
auto abs_DC = 2.0 * abs(in[0]) - abs(in[1]);
auto phase_DC = 2.0 * arg(in[0]) - arg(in[1]);
auto DC = polar(abs_DC, phase_DC);
vector<complex<double>> ret;
ret.push_back(DC);
// add non-symmetric part
ret.insert(ret.end(), in.begin(), in.end());
// add flipped complex conjugate values
for(auto it = in.rbegin(); it != in.rend(); it++) {
ret.push_back(conj(*it));
}
return ret;
};
auto makeRealAndScale = [](vector<complex<double>> &in) {
for(unsigned int i=0;i<in.size();i++) {
in[i] = real(in[i]) / in.size();
}
};
// S parameter error boxes
vector<Sparam> data_side1, data_side2;
{
auto p112x = makeSymmetric(S11);
auto p212x = makeSymmetric(S21);
// transform into time domain and calculate step responses
auto t112x = p112x;
Fft::transform(t112x, true);
makeRealAndScale(t112x);
Fft::shift(t112x, false);
partial_sum(t112x.begin(), t112x.end(), t112x.begin());
auto t212x = p212x;
Fft::transform(t212x, true);
makeRealAndScale(t212x);
Fft::shift(t212x, false);
partial_sum(t212x.begin(), t212x.end(), t212x.begin());
// find the midpoint of the trace
auto mid = lower_bound(t212x.begin(), t212x.end(), 0.5, [](complex<double> p, double c) -> bool {
return real(p) < c;
}) - t212x.begin();
// mask step response
vector<complex<double>> t111xStep(2*n + 1, 0.0);
copy(t112x.begin() + n, t112x.begin() + mid, t111xStep.begin() + n);
Fft::shift(t111xStep, true);
// create impulse response from masked step response
adjacent_difference(t111xStep.begin(), t111xStep.end(), t111xStep.begin());
Fft::transform(t111xStep, false);
auto &p111x = t111xStep;
// calculate p221x and p211x
vector<complex<double>> p221x;
vector<complex<double>> p211x;
double k = 1.0;
complex<double> test, last_test;
for(unsigned int i=0;i<p112x.size();i++) {
p221x.push_back((p112x[i]-p111x[i])/p212x[i]);
test = sqrt(p212x[i]*(1.0-p221x[i]*p221x[i]));
if(i > 0) {
if(arg(test) - arg(last_test) > 0) {
k = -k;
}
}
last_test = test;
p211x.push_back(k*test);
}
// create S parameter errorbox
for(unsigned int i=1;i<=n;i++) {
data_side1.push_back(Sparam(p111x[i], p211x[i], p211x[i], p221x[i]));
}
}
// same thing for error box 2. Variable names get a bit confusing because they are viewed from port 2 (S22 is now called p112x, ...).
// All variable names follow https://gitlab.com/IEEE-SA/ElecChar/P370/-/blob/master/TG1/IEEEP3702xThru_Octave.m
{
auto p112x = makeSymmetric(S22);
auto p212x = makeSymmetric(S12);
// transform into time domain and calculate step responses
auto t112x = p112x;
Fft::transform(t112x, true);
makeRealAndScale(t112x);
Fft::shift(t112x, false);
partial_sum(t112x.begin(), t112x.end(), t112x.begin());
auto t212x = p212x;
Fft::transform(t212x, true);
makeRealAndScale(t212x);
Fft::shift(t212x, false);
partial_sum(t212x.begin(), t212x.end(), t212x.begin());
// find the midpoint of the trace
auto mid = lower_bound(t212x.begin(), t212x.end(), 0.5, [](complex<double> p, double c) -> bool {
return real(p) < c;
}) - t212x.begin();
// mask step response
vector<complex<double>> t111xStep(2*n + 1, 0.0);
copy(t112x.begin() + n, t112x.begin() + mid, t111xStep.begin() + n);
Fft::shift(t111xStep, true);
// create impulse response from masked step response
adjacent_difference(t111xStep.begin(), t111xStep.end(), t111xStep.begin());
Fft::transform(t111xStep, false);
auto &p111x = t111xStep;
// calculate p221x and p211x
vector<complex<double>> p221x;
vector<complex<double>> p211x;
double k = 1.0;
complex<double> test, last_test;
for(unsigned int i=0;i<p112x.size();i++) {
p221x.push_back((p112x[i]-p111x[i])/p212x[i]);
test = sqrt(p212x[i]*(1.0-p221x[i]*p221x[i]));
if(i > 0) {
if(arg(test) - arg(last_test) > 0) {
k = -k;
}
}
last_test = test;
p211x.push_back(k*test);
}
// create S parameter errorbox
for(unsigned int i=1;i<=n;i++) {
data_side2.push_back(Sparam(p111x[i], p211x[i], p211x[i], data_side1[i-1].m22));
data_side1[i-1].m22 = p221x[i];
}
}
// got the error boxes, convert to T parameters and invert
for(unsigned int i=0;i<n;i++) {
Point p;
p.freq = f[i];
p.inverseP1 = Tparam(data_side1[i]).inverse();
p.inverseP2 = Tparam(data_side2[i]).inverse();
points.push_back(p);
}
measurements.clear();
if(msgBox) {
msgBox->accept();
msgBox = nullptr;
}
updateLabel();
} else if(measurements.size() > 0 || p.pointNum == 0) {
measurements.push_back(p);
}
}
// correct measurement
if(points.size() > 0) {
if(p.frequency != 0 && (p.frequency < points.front().freq || p.frequency > points.back().freq)) {
// No exact match, measurement no longer valid
points.clear();
InformationBox::ShowMessage("Warning", "2xThru measurement cleared because it no longer matches the selected span");
return;
}
// find correct measurement point
auto point = lower_bound(points.begin(), points.end(), p.frequency, [](Point p, uint64_t freq) -> bool {
return p.freq < freq;
});
Tparam inv1, inv2;
if(point->freq == p.frequency) {
inv1 = point->inverseP1;
inv2 = point->inverseP2;
} else {
// need to interpolate
auto high = point;
point--;
auto low = point;
double alpha = (p.frequency - low->freq) / (high->freq - low->freq);
inv1 = low->inverseP1 * (1 - alpha) + high->inverseP1 * alpha;
inv2 = low->inverseP2 * (1 - alpha) + high->inverseP2 * alpha;
}
// perform correction
Tparam corrected = inv1*meas*inv2;
// transform back into S parameters
Sparam S(corrected);
p.real_S11 = real(S.m11);
p.imag_S11 = imag(S.m11);
p.real_S12 = real(S.m12);
p.imag_S12 = imag(S.m12);
p.real_S21 = real(S.m21);
p.imag_S21 = imag(S.m21);
p.real_S22 = real(S.m22);
p.imag_S22 = imag(S.m22);
}
}
void TwoThru::startMeasurement()
{
points.clear();
measurements.clear();
updateLabel();
msgBox = new QMessageBox(QMessageBox::Information, "2xThru", "Taking measurement...", QMessageBox::Cancel);
connect(msgBox, &QMessageBox::rejected, [=]() {
measuring = false;
points.clear();
measurements.clear();
updateLabel();
});
msgBox->show();
measuring = true;
}
void TwoThru::updateLabel()
{
if(points.size() > 0) {
ui->lInfo->setText("Got "+QString::number(points.size())+" points");
} else {
ui->lInfo->setText("No measurement, not deembedding");
}
}
void TwoThru::edit()
{
auto dialog = new QDialog();
ui = new Ui::TwoThruDialog();
ui->setupUi(dialog);
connect(ui->bMeasure, &QPushButton::clicked, this, &TwoThru::startMeasurement);
connect(ui->buttonBox, &QDialogButtonBox::accepted, dialog, &QDialog::accept);
updateLabel();
dialog->show();
}
nlohmann::json TwoThru::toJSON()
{
nlohmann::json j;
for(auto p : points) {
nlohmann::json jp;
jp["frequency"] = p.freq;
jp["p1_11_r"] = p.inverseP1.m11.real();
jp["p1_11_i"] = p.inverseP1.m11.imag();
jp["p1_12_r"] = p.inverseP1.m12.real();
jp["p1_12_i"] = p.inverseP1.m12.imag();
jp["p1_21_r"] = p.inverseP1.m21.real();
jp["p1_21_i"] = p.inverseP1.m21.imag();
jp["p1_22_r"] = p.inverseP1.m22.real();
jp["p1_22_i"] = p.inverseP1.m22.imag();
jp["p2_11_r"] = p.inverseP2.m11.real();
jp["p2_11_i"] = p.inverseP2.m11.imag();
jp["p2_12_r"] = p.inverseP2.m12.real();
jp["p2_12_i"] = p.inverseP2.m12.imag();
jp["p2_21_r"] = p.inverseP2.m21.real();
jp["p2_21_i"] = p.inverseP2.m21.imag();
jp["p2_22_r"] = p.inverseP2.m22.real();
jp["p2_22_i"] = p.inverseP2.m22.imag();
j.push_back(jp);
}
return j;
}
void TwoThru::fromJSON(nlohmann::json j)
{
points.clear();
for(auto jp : j) {
Point p;
p.freq = jp.value("frequency", 0.0);
p.inverseP1.m11 = complex<double>(jp.value("p1_11_r", 0.0), jp.value("p1_11_i", 0.0));
p.inverseP1.m12 = complex<double>(jp.value("p1_12_r", 0.0), jp.value("p1_12_i", 0.0));
p.inverseP1.m21 = complex<double>(jp.value("p1_21_r", 0.0), jp.value("p1_21_i", 0.0));
p.inverseP1.m22 = complex<double>(jp.value("p1_22_r", 0.0), jp.value("p1_22_i", 0.0));
p.inverseP2.m11 = complex<double>(jp.value("p2_11_r", 0.0), jp.value("p2_11_i", 0.0));
p.inverseP2.m12 = complex<double>(jp.value("p2_12_r", 0.0), jp.value("p2_12_i", 0.0));
p.inverseP2.m21 = complex<double>(jp.value("p2_21_r", 0.0), jp.value("p2_21_i", 0.0));
p.inverseP2.m22 = complex<double>(jp.value("p2_22_r", 0.0), jp.value("p2_22_i", 0.0));
points.push_back(p);
}
}