LibreVNA/Software/PC_Application/Calibration/calibration.cpp

672 lines
28 KiB
C++

#include "calibration.h"
#include <algorithm>
#include <QMessageBox>
#include <QFileDialog>
#include <fstream>
using namespace std;
Calibration::Calibration()
{
// Creator vectors for measurements
measurements[Measurement::Port1Open].datapoints = vector<Protocol::Datapoint>();
measurements[Measurement::Port1Short].datapoints = vector<Protocol::Datapoint>();
measurements[Measurement::Port1Load].datapoints = vector<Protocol::Datapoint>();
measurements[Measurement::Port2Open].datapoints = vector<Protocol::Datapoint>();
measurements[Measurement::Port2Short].datapoints = vector<Protocol::Datapoint>();
measurements[Measurement::Port2Load].datapoints = vector<Protocol::Datapoint>();
measurements[Measurement::Isolation].datapoints = vector<Protocol::Datapoint>();
measurements[Measurement::Through].datapoints = vector<Protocol::Datapoint>();
type = Type::None;
}
void Calibration::clearMeasurements()
{
for(auto m : measurements) {
m.second.datapoints.clear();
}
}
void Calibration::clearMeasurement(Calibration::Measurement type)
{
measurements[type].datapoints.clear();
measurements[type].timestamp = QDateTime();
}
void Calibration::addMeasurement(Calibration::Measurement type, Protocol::Datapoint &d)
{
measurements[type].datapoints.push_back(d);
measurements[type].timestamp = QDateTime::currentDateTime();
}
bool Calibration::calculationPossible(Calibration::Type type)
{
std::vector<Measurement> requiredMeasurements;
switch(type) {
case Type::Port1SOL:
requiredMeasurements.push_back(Measurement::Port1Open);
requiredMeasurements.push_back(Measurement::Port1Short);
requiredMeasurements.push_back(Measurement::Port1Load);
break;
case Type::Port2SOL:
requiredMeasurements.push_back(Measurement::Port2Open);
requiredMeasurements.push_back(Measurement::Port2Short);
requiredMeasurements.push_back(Measurement::Port2Load);
break;
case Type::FullSOLT:
requiredMeasurements.push_back(Measurement::Port1Open);
requiredMeasurements.push_back(Measurement::Port1Short);
requiredMeasurements.push_back(Measurement::Port1Load);
requiredMeasurements.push_back(Measurement::Port2Open);
requiredMeasurements.push_back(Measurement::Port2Short);
requiredMeasurements.push_back(Measurement::Port2Load);
requiredMeasurements.push_back(Measurement::Through);
break;
case Type::None:
return false;
}
return SanityCheckSamples(requiredMeasurements);
}
bool Calibration::constructErrorTerms(Calibration::Type type)
{
if(!calculationPossible(type)) {
return false;
}
if(minFreq < kit.minFreq() || maxFreq > kit.maxFreq()) {
// Calkit does not support complete calibration range
QMessageBox::critical(nullptr, "Unable to perform calibration", "The calibration kit does not support the complete span. Please choose a different calibration kit or a narrower span.");
return false;
}
switch(type) {
case Type::Port1SOL:
constructPort1SOL();
break;
case Type::Port2SOL:
constructPort2SOL();
break;
case Type::FullSOLT:
construct12TermPoints();
break;
case Type::None:
break;
}
this->type = type;
return true;
}
void Calibration::resetErrorTerms()
{
type = Type::None;
points.clear();
}
void Calibration::construct12TermPoints()
{
std::vector<Measurement> requiredMeasurements;
requiredMeasurements.push_back(Measurement::Port1Open);
requiredMeasurements.push_back(Measurement::Port1Short);
requiredMeasurements.push_back(Measurement::Port1Load);
requiredMeasurements.push_back(Measurement::Port2Open);
requiredMeasurements.push_back(Measurement::Port2Short);
requiredMeasurements.push_back(Measurement::Port2Load);
requiredMeasurements.push_back(Measurement::Through);
if(!SanityCheckSamples(requiredMeasurements)) {
throw runtime_error("Missing/wrong calibration measurement");
}
requiredMeasurements.push_back(Measurement::Isolation);
bool isolation_measured = SanityCheckSamples(requiredMeasurements);
// If we get here the calibration measurements are all okay
points.clear();
for(unsigned int i = 0;i<measurements[Measurement::Port1Open].datapoints.size();i++) {
Point p;
p.frequency = measurements[Measurement::Port1Open].datapoints[i].frequency;
// extract required complex reflection/transmission factors from datapoints
auto S11_open = complex<double>(measurements[Measurement::Port1Open].datapoints[i].real_S11, measurements[Measurement::Port1Open].datapoints[i].imag_S11);
auto S11_short = complex<double>(measurements[Measurement::Port1Short].datapoints[i].real_S11, measurements[Measurement::Port1Short].datapoints[i].imag_S11);
auto S11_load = complex<double>(measurements[Measurement::Port1Load].datapoints[i].real_S11, measurements[Measurement::Port1Load].datapoints[i].imag_S11);
auto S22_open = complex<double>(measurements[Measurement::Port2Open].datapoints[i].real_S22, measurements[Measurement::Port2Open].datapoints[i].imag_S22);
auto S22_short = complex<double>(measurements[Measurement::Port2Short].datapoints[i].real_S22, measurements[Measurement::Port2Short].datapoints[i].imag_S22);
auto S22_load = complex<double>(measurements[Measurement::Port2Load].datapoints[i].real_S22, measurements[Measurement::Port2Load].datapoints[i].imag_S22);
auto S21_isolation = complex<double>(0,0);
auto S12_isolation = complex<double>(0,0);
if(isolation_measured) {
S21_isolation = complex<double>(measurements[Measurement::Isolation].datapoints[i].real_S21, measurements[Measurement::Isolation].datapoints[i].imag_S21);
S12_isolation = complex<double>(measurements[Measurement::Isolation].datapoints[i].real_S12, measurements[Measurement::Isolation].datapoints[i].imag_S12);
}
auto S11_through = complex<double>(measurements[Measurement::Through].datapoints[i].real_S11, measurements[Measurement::Through].datapoints[i].imag_S11);
auto S21_through = complex<double>(measurements[Measurement::Through].datapoints[i].real_S21, measurements[Measurement::Through].datapoints[i].imag_S21);
auto S22_through = complex<double>(measurements[Measurement::Through].datapoints[i].real_S22, measurements[Measurement::Through].datapoints[i].imag_S22);
auto S12_through = complex<double>(measurements[Measurement::Through].datapoints[i].real_S12, measurements[Measurement::Through].datapoints[i].imag_S12);
auto actual = kit.toReflection(p.frequency);
// Forward calibration
computeSOL(S11_short, S11_open, S11_load, p.fe00, p.fe11, p.fe10e01, actual.Open, actual.Short, actual.Load);
p.fe30 = S21_isolation;
// See page 17 of http://www2.electron.frba.utn.edu.ar/~jcecconi/Bibliografia/04%20-%20Param_S_y_VNA/Network_Analyzer_Error_Models_and_Calibration_Methods.pdf
// Formulas for S11M and S21M solved for e22 and e10e32
auto deltaS = actual.ThroughS11*actual.ThroughS22 - actual.ThroughS21 * actual.ThroughS12;
p.fe22 = ((S11_through - p.fe00)*(1.0 - p.fe11 * actual.ThroughS11)-actual.ThroughS11*p.fe10e01)
/ ((S11_through - p.fe00)*(actual.ThroughS22-p.fe11*deltaS)-deltaS*p.fe10e01);
p.fe10e32 = (S21_through - p.fe30)*(1.0 - p.fe11*actual.ThroughS11 - p.fe22*actual.ThroughS22 + p.fe11*p.fe22*deltaS) / actual.ThroughS21;
// Reverse calibration
computeSOL(S22_short, S22_open, S22_load, p.re33, p.re22, p.re23e32, actual.Open, actual.Short, actual.Load);
p.re03 = S12_isolation;
p.re11 = ((S22_through - p.re33)*(1.0 - p.re22 * actual.ThroughS22)-actual.ThroughS22*p.re23e32)
/ ((S22_through - p.re33)*(actual.ThroughS11-p.re22*deltaS)-deltaS*p.re23e32);
p.re23e01 = (S12_through - p.re03)*(1.0 - p.re11*actual.ThroughS11 - p.re22*actual.ThroughS22 + p.re11*p.re22*deltaS) / actual.ThroughS12;
points.push_back(p);
}
}
void Calibration::constructPort1SOL()
{
std::vector<Measurement> requiredMeasurements;
requiredMeasurements.push_back(Measurement::Port1Open);
requiredMeasurements.push_back(Measurement::Port1Short);
requiredMeasurements.push_back(Measurement::Port1Load);
if(!SanityCheckSamples(requiredMeasurements)) {
throw runtime_error("Missing/wrong calibration measurement");
}
// If we get here the calibration measurements are all okay
points.clear();
for(unsigned int i = 0;i<measurements[Measurement::Port1Open].datapoints.size();i++) {
Point p;
p.frequency = measurements[Measurement::Port1Open].datapoints[i].frequency;
// extract required complex reflection/transmission factors from datapoints
auto S11_open = complex<double>(measurements[Measurement::Port1Open].datapoints[i].real_S11, measurements[Measurement::Port1Open].datapoints[i].imag_S11);
auto S11_short = complex<double>(measurements[Measurement::Port1Short].datapoints[i].real_S11, measurements[Measurement::Port1Short].datapoints[i].imag_S11);
auto S11_load = complex<double>(measurements[Measurement::Port1Load].datapoints[i].real_S11, measurements[Measurement::Port1Load].datapoints[i].imag_S11);
// OSL port1
auto actual = kit.toReflection(p.frequency);
// See page 19 of http://www2.electron.frba.utn.edu.ar/~jcecconi/Bibliografia/04%20-%20Param_S_y_VNA/Network_Analyzer_Error_Models_and_Calibration_Methods.pdf
computeSOL(S11_short, S11_open, S11_load, p.fe00, p.fe11, p.fe10e01, actual.Open, actual.Short, actual.Load);
// All other calibration coefficients to ideal values
p.fe30 = 0.0;
p.fe22 = 0.0;
p.fe10e32 = 1.0;
p.re33 = 0.0;
p.re22 = 0.0;
p.re23e32 = 1.0;
p.re03 = 0.0;
p.re11 = 0.0;
p.re23e01 = 1.0;
points.push_back(p);
}
}
void Calibration::constructPort2SOL()
{
std::vector<Measurement> requiredMeasurements;
requiredMeasurements.push_back(Measurement::Port2Open);
requiredMeasurements.push_back(Measurement::Port2Short);
requiredMeasurements.push_back(Measurement::Port2Load);
if(!SanityCheckSamples(requiredMeasurements)) {
throw runtime_error("Missing/wrong calibration measurement");
}
// If we get here the calibration measurements are all okay
points.clear();
for(unsigned int i = 0;i<measurements[Measurement::Port2Open].datapoints.size();i++) {
Point p;
p.frequency = measurements[Measurement::Port2Open].datapoints[i].frequency;
// extract required complex reflection/transmission factors from datapoints
auto S22_open = complex<double>(measurements[Measurement::Port2Open].datapoints[i].real_S22, measurements[Measurement::Port2Open].datapoints[i].imag_S22);
auto S22_short = complex<double>(measurements[Measurement::Port2Short].datapoints[i].real_S22, measurements[Measurement::Port2Short].datapoints[i].imag_S22);
auto S22_load = complex<double>(measurements[Measurement::Port2Load].datapoints[i].real_S22, measurements[Measurement::Port2Load].datapoints[i].imag_S22);
// OSL port2
auto actual = kit.toReflection(p.frequency);
// See page 19 of http://www2.electron.frba.utn.edu.ar/~jcecconi/Bibliografia/04%20-%20Param_S_y_VNA/Network_Analyzer_Error_Models_and_Calibration_Methods.pdf
computeSOL(S22_short, S22_open, S22_load, p.re33, p.re22, p.re23e32, actual.Open, actual.Short, actual.Load);
// All other calibration coefficients to ideal values
p.fe30 = 0.0;
p.fe22 = 0.0;
p.fe10e32 = 1.0;
p.fe00 = 0.0;
p.fe11 = 0.0;
p.fe10e01 = 1.0;
p.re03 = 0.0;
p.re11 = 0.0;
p.re23e01 = 1.0;
points.push_back(p);
}
}
void Calibration::correctMeasurement(Protocol::Datapoint &d)
{
if(type == Type::None) {
// No calibration data, do nothing
return;
}
// Convert measurements to complex variables
auto S11m = complex<double>(d.real_S11, d.imag_S11);
auto S21m = complex<double>(d.real_S21, d.imag_S21);
auto S22m = complex<double>(d.real_S22, d.imag_S22);
auto S12m = complex<double>(d.real_S12, d.imag_S12);
// find correct entry
auto p = getCalibrationPoint(d);
// equations from page 20 of http://www2.electron.frba.utn.edu.ar/~jcecconi/Bibliografia/04%20-%20Param_S_y_VNA/Network_Analyzer_Error_Models_and_Calibration_Methods.pdf
auto denom = (1.0 + (S11m - p.fe00) / p.fe10e01 * p.fe11) * (1.0 + (S22m - p.re33) / p.re23e32 * p.re22)
- (S21m - p.fe30) / p.fe10e32 * (S12m - p.re03) / p.re23e01 * p.fe22 * p.re11;
auto S11 = ((S11m - p.fe00) / p.fe10e01 * (1.0 + (S22m - p.re33) / p.re23e32 * p.re22)
- p.fe22 * (S21m - p.fe30) / p.fe10e32 * (S12m - p.re03) / p.re23e01) / denom;
auto S21 = ((S21m - p.fe30) / p.fe10e32 * (1.0 + (S22m - p.re33) / p.re23e32 * (p.re22 - p.fe22))) / denom;
auto S22 = ((S22m - p.re33) / p.re23e32 * (1.0 + (S11m - p.fe00) / p.fe10e01 * p.fe11)
- p.re11 * (S21m - p.fe30) / p.fe10e32 * (S12m - p.re03) / p.re23e01) / denom;
auto S12 = ((S12m - p.re03) / p.re23e01 * (1.0 + (S11m - p.fe00) / p.fe10e01 * (p.fe11 - p.re11))) / denom;
d.real_S11 = S11.real();
d.imag_S11 = S11.imag();
d.real_S12 = S12.real();
d.imag_S12 = S12.imag();
d.real_S21 = S21.real();
d.imag_S21 = S21.imag();
d.real_S22 = S22.real();
d.imag_S22 = S22.imag();
}
Calibration::InterpolationType Calibration::getInterpolation(Protocol::SweepSettings settings)
{
if(!points.size()) {
return InterpolationType::NoCalibration;
}
if(settings.f_start < points.front().frequency || settings.f_stop > points.back().frequency) {
return InterpolationType::Extrapolate;
}
// Either exact or interpolation, check individual frequencies
uint32_t f_step;
if(settings.points > 1) {
f_step = (settings.f_stop - settings.f_start) / (settings.points - 1);
} else {
f_step = settings.f_stop - settings.f_start;
}
for(uint64_t f = settings.f_start; f <= settings.f_stop; f += f_step) {
if(find_if(points.begin(), points.end(), [&f](const Point& p){
return abs(f - p.frequency) < 100;
}) == points.end()) {
return InterpolationType::Interpolate;
}
}
// if we get here all frequency points were matched
if(points.front().frequency == settings.f_start && points.back().frequency == settings.f_stop) {
return InterpolationType::Unchanged;
} else {
return InterpolationType::Exact;
}
}
QString Calibration::MeasurementToString(Calibration::Measurement m)
{
switch(m) {
case Measurement::Port1Open:
return "Port 1 Open";
case Measurement::Port1Short:
return "Port 1 Short";
case Measurement::Port1Load:
return "Port 1 Load";
case Measurement::Port2Open:
return "Port 2 Open";
case Measurement::Port2Short:
return "Port 2 Short";
case Measurement::Port2Load:
return "Port 2 Load";
case Measurement::Through:
return "Through";
case Measurement::Isolation:
return "Isolation";
default:
return "Unknown";
}
}
QString Calibration::TypeToString(Calibration::Type t)
{
switch(t) {
case Type::Port1SOL: return "Port 1"; break;
case Type::Port2SOL: return "Port 2"; break;
case Type::FullSOLT: return "SOLT"; break;
default: return "None"; break;
}
}
const std::vector<Calibration::Type> Calibration::Types()
{
const std::vector<Calibration::Type> ret = {Type::Port1SOL, Type::Port2SOL, Type::FullSOLT};
return ret;
}
const std::vector<Calibration::Measurement> Calibration::Measurements(Calibration::Type type)
{
switch(type) {
case Type::FullSOLT:
case Type::None:
return {Measurement::Port1Short, Measurement::Port1Open, Measurement::Port1Load, Measurement::Port2Short, Measurement::Port2Open, Measurement::Port2Load, Measurement::Through, Measurement::Isolation};
break;
case Type::Port1SOL:
return {Measurement::Port1Short, Measurement::Port1Open, Measurement::Port1Load};
break;
case Type::Port2SOL:
return {Measurement::Port2Short, Measurement::Port2Open, Measurement::Port2Load};
break;
default:
return {};
break;
}
}
Calibration::MeasurementInfo Calibration::getMeasurementInfo(Calibration::Measurement m)
{
MeasurementInfo info;
switch(m) {
case Measurement::Port1Short:
info.name = "Port 1 short";
info.prerequisites = "Short standard connected to port 1, port 2 open";
break;
case Measurement::Port1Open:
info.name = "Port 1 open";
info.prerequisites = "Open standard connected to port 1, port 2 open";
break;
case Measurement::Port1Load:
info.name = "Port 1 load";
info.prerequisites = "Load standard connected to port 1, port 2 open";
break;
case Measurement::Port2Short:
info.name = "Port 2 short";
info.prerequisites = "Port 1 open, short standard connected to port 2";
break;
case Measurement::Port2Open:
info.name = "Port 2 open";
info.prerequisites = "Port 1 open, open standard connected to port 2";
break;
case Measurement::Port2Load:
info.name = "Port 2 load";
info.prerequisites = "Port 1 open, load standard connected to port 2";
break;
case Measurement::Through:
info.name = "Through";
info.prerequisites = "Port 1 connected to port 2 via through standard";
break;
case Measurement::Isolation:
info.name = "Isolation";
info.prerequisites = "Both ports terminated into 50 ohm";
}
info.points = measurements[m].datapoints.size();
if(info.points > 0) {
info.fmin = measurements[m].datapoints.front().frequency;
info.fmax = measurements[m].datapoints.back().frequency;
info.points = measurements[m].datapoints.size();
}
info.timestamp = measurements[m].timestamp;
return info;
}
std::vector<Trace *> Calibration::getErrorTermTraces()
{
std::vector<Trace*> traces;
const QString traceNames[12] = {"e00", "F_e11", "e10e01", "e10e32", "F_e22", "e30", "e33", "R_e11", "e23e32", "e23e01", "R_e22", "e03"};
constexpr bool reflection[12] = {true, true, false, false, true, false, true, true, false, false, true, false};
for(int i=0;i<12;i++) {
auto t = new Trace(traceNames[i], Qt::red);
t->setCalibration(true);
t->setReflection(reflection[i]);
traces.push_back(t);
}
for(auto p : points) {
Trace::Data d;
d.frequency = p.frequency;
for(int i=0;i<12;i++) {
switch(i) {
case 0: d.S = p.fe00; break;
case 1: d.S = p.fe11; break;
case 2: d.S = p.fe10e01; break;
case 3: d.S = p.fe10e32; break;
case 4: d.S = p.fe22; break;
case 5: d.S = p.fe30; break;
case 6: d.S = p.re33; break;
case 7: d.S = p.re11; break;
case 8: d.S = p.re23e32; break;
case 9: d.S = p.re23e01; break;
case 10: d.S = p.re22; break;
case 11: d.S = p.re03; break;
}
traces[i]->addData(d);
}
}
return traces;
}
bool Calibration::openFromFile(QString filename)
{
if(filename.isEmpty()) {
filename = QFileDialog::getOpenFileName(nullptr, "Load calibration data", "", "Calibration files (*.cal)", nullptr, QFileDialog::DontUseNativeDialog);
if(filename.isEmpty()) {
// aborted selection
return false;
}
}
// attempt to load associated calibration kit first (needs to be available when performing calibration)
auto calkit_file = filename;
auto dotPos = calkit_file.lastIndexOf('.');
if(dotPos >= 0) {
calkit_file.truncate(dotPos);
}
calkit_file.append(".calkit");
try {
kit = Calkit::fromFile(calkit_file.toStdString());
} catch (runtime_error e) {
QMessageBox::warning(nullptr, "Missing calibration kit", "The calibration kit file associated with the selected calibration could not be parsed. The calibration might not be accurate. (" + QString(e.what()) + ")");
}
ifstream file;
file.open(filename.toStdString());
try {
file >> *this;
} catch(runtime_error e) {
QMessageBox::warning(nullptr, "File parsing error", e.what());
return false;
}
return true;
}
bool Calibration::saveToFile(QString filename)
{
if(filename.isEmpty()) {
filename = QFileDialog::getSaveFileName(nullptr, "Save calibration data", "", "Calibration files (*.cal)", nullptr, QFileDialog::DontUseNativeDialog);
if(filename.isEmpty()) {
// aborted selection
return false;
}
}
// strip any potential file name extension and set default
auto dotPos = filename.lastIndexOf('.');
if(dotPos >= 0) {
filename.truncate(dotPos);
}
auto calibration_file = filename;
calibration_file.append(".cal");
ofstream file;
file.open(calibration_file.toStdString());
file << *this;
auto calkit_file = filename;
calkit_file.append(".calkit");
kit.toFile(calkit_file.toStdString());
return true;
}
ostream& operator<<(ostream &os, const Calibration &c)
{
for(auto m : c.measurements) {
if(m.second.datapoints.size() > 0) {
os << c.MeasurementToString(m.first).toStdString() << endl;
os << m.second.timestamp.toSecsSinceEpoch() << endl;
os << m.second.datapoints.size() << endl;
for(auto p : m.second.datapoints) {
os << p.pointNum << " " << p.frequency << " ";
os << p.imag_S11 << " " << p.real_S11 << " " << p.imag_S21 << " " << p.real_S21 << " " << p.imag_S12 << " " << p.real_S12 << " " << p.imag_S22 << " " << p.real_S22;
os << endl;
}
}
}
os << Calibration::TypeToString(c.getType()).toStdString() << endl;
return os;
}
istream& operator >>(istream &in, Calibration &c)
{
std::string line;
while(getline(in, line)) {
for(auto m : Calibration::Measurements()) {
if(Calibration::MeasurementToString(m) == QString::fromStdString(line)) {
// this is the correct measurement
c.clearMeasurement(m);
uint timestamp;
in >> timestamp;
c.measurements[m].timestamp = QDateTime::fromSecsSinceEpoch(timestamp);
unsigned int points;
in >> points;
for(unsigned int i=0;i<points;i++) {
Protocol::Datapoint p;
in >> p.pointNum >> p.frequency;
in >> p.imag_S11 >> p.real_S11 >> p.imag_S21 >> p.real_S21 >> p.imag_S12 >> p.real_S12 >> p.imag_S22 >> p.real_S22;
c.measurements[m].datapoints.push_back(p);
if(in.eof() || in.bad() || in.fail()) {
c.clearMeasurement(m);
throw runtime_error("Failed to parse measurement \"" + line + "\", aborting calibration data import.");
}
}
break;
}
}
for(auto t : Calibration::Types()) {
if(Calibration::TypeToString(t) == QString::fromStdString(line)) {
// try to apply this calibration type
if(c.calculationPossible(t)) {
c.constructErrorTerms(t);
} else {
throw runtime_error("Incomplete calibration data, the requested \"" + line + "\"-Calibration could not be performed.");
}
break;
}
}
}
return in;
}
bool Calibration::SanityCheckSamples(std::vector<Calibration::Measurement> &requiredMeasurements)
{
// sanity check measurements, all need to be of the same size with the same frequencies (except for isolation which may be empty)
vector<uint64_t> freqs;
for(auto type : requiredMeasurements) {
auto m = measurements[type];
if(m.datapoints.size() == 0) {
// empty required measurement
return false;
}
if(freqs.size() == 0) {
// this is the first measurement, create frequency vector
for(auto p : m.datapoints) {
freqs.push_back(p.frequency);
}
} else {
// compare with already assembled frequency vector
if(m.datapoints.size() != freqs.size()) {
return false;
}
for(unsigned int i=0;i<freqs.size();i++) {
if(m.datapoints[i].frequency != freqs[i]) {
return false;
}
}
}
}
minFreq = freqs.front();
maxFreq = freqs.back();
return true;
}
Calibration::Point Calibration::getCalibrationPoint(Protocol::Datapoint &d)
{
if(!points.size()) {
throw runtime_error("No calibration points available");
}
if(d.frequency <= points.front().frequency) {
// use first point even for lower frequencies
return points.front();
}
if(d.frequency >= points.back().frequency) {
// use last point even for higher frequencies
return points.back();
}
auto p = lower_bound(points.begin(), points.end(), d.frequency, [](Point p, uint64_t freq) -> bool {
return p.frequency < freq;
});
if(p->frequency == d.frequency) {
// Exact match, return point
return *p;
}
// need to interpolate
auto high = p;
p--;
auto low = p;
double alpha = (d.frequency - low->frequency) / (high->frequency - low->frequency);
Point ret;
ret.frequency = d.frequency;
ret.fe00 = low->fe00 * (1 - alpha) + high->fe00 * alpha;
ret.fe11 = low->fe11 * (1 - alpha) + high->fe11 * alpha;
ret.fe22 = low->fe22 * (1 - alpha) + high->fe22 * alpha;
ret.fe30 = low->fe30 * (1 - alpha) + high->fe30 * alpha;
ret.re03 = low->re03 * (1 - alpha) + high->re03 * alpha;
ret.re11 = low->re11 * (1 - alpha) + high->re11 * alpha;
ret.re22 = low->re22 * (1 - alpha) + high->re22 * alpha;
ret.re33 = low->re33 * (1 - alpha) + high->re33 * alpha;
ret.fe10e01 = low->fe10e01 * (1 - alpha) + high->fe10e01 * alpha;
ret.fe10e32 = low->fe10e32 * (1 - alpha) + high->fe10e32 * alpha;
ret.re23e01 = low->re23e01 * (1 - alpha) + high->re23e01 * alpha;
ret.re23e32 = low->re23e32 * (1 - alpha) + high->re23e32 * alpha;
return ret;
}
void Calibration::computeSOL(std::complex<double> s_m, std::complex<double> o_m, std::complex<double> l_m,
std::complex<double> &directivity, std::complex<double> &match, std::complex<double> &tracking,
std::complex<double> o_c, std::complex<double> s_c, std::complex<double> l_c)
{
// equations from page 13 of http://www2.electron.frba.utn.edu.ar/~jcecconi/Bibliografia/04%20-%20Param_S_y_VNA/Network_Analyzer_Error_Models_and_Calibration_Methods.pdf
// solved while taking non ideal o/s/l standards into account
auto denom = l_c * o_c * (o_m - l_m) + l_c * s_c * (l_m - s_m) + o_c * s_c * (s_m - o_m);
directivity = (l_c * o_m * (s_m * (o_c - s_c) + l_m * s_c) - l_c * o_c * l_m * s_m + o_c * l_m * s_c * (s_m - o_m)) / denom;
match = (l_c * (o_m - s_m) + o_c * (s_m - l_m) + s_c * (l_m - o_m)) / denom;
auto delta = (l_c * l_m * (o_m - s_m) + o_c * o_m * (s_m - l_m) + s_c * s_m * (l_m - o_m)) / denom;
tracking = directivity * match - delta;
}
std::complex<double> Calibration::correctSOL(std::complex<double> measured, std::complex<double> directivity, std::complex<double> match, std::complex<double> tracking)
{
return (measured - directivity) / (measured * match - directivity * match + tracking);
}
Calkit &Calibration::getCalibrationKit()
{
return kit;
}
void Calibration::setCalibrationKit(const Calkit &value)
{
kit = value;
}
Calibration::Type Calibration::getType() const
{
return type;
}