LibreVNA/Software/PC_Application/Calibration/calkit.cpp
2020-08-30 22:03:41 +02:00

291 lines
8.7 KiB
C++

#include "calkit.h"
#include <fstream>
#include <iomanip>
#include "calkitdialog.h"
#include <math.h>
using namespace std;
Calkit::Calkit()
: ts_open(nullptr),
ts_short(nullptr),
ts_load(nullptr),
ts_through(nullptr),
ts_cached(false)
{
open_Z0 = 50.0;
open_delay = 0.0;
open_loss = 0.0;
open_C0 = 0.0;
open_C1 = 0.0;
open_C2 = 0.0;
open_C3 = 0.0;
short_Z0 = 50.0;
short_delay = 0.0;
short_loss = 0.0;
short_L0 = 0.0;
short_L1 = 0.0;
short_L2 = 0.0;
short_L3 = 0.0;
load_Z0 = 50.0;
through_Z0 = 50.0;
through_delay = 0.0;
through_loss = 0.0;
open_measurements = false;
short_measurements = false;
load_measurements = false;
through_measurements = false;
open_file = "";
short_file = "";
load_file = "";
through_file = "";
open_Sparam = 0;
short_Sparam = 0;
load_Sparam = 0;
through_Sparam1 = 0;
through_Sparam2 = 1;
}
void Calkit::toFile(std::string filename)
{
ofstream file;
file.open(filename);
file << std::fixed << std::setprecision(12);
file << open_measurements << "\n" << short_measurements << "\n" << load_measurements << "\n" << through_measurements << "\n";
file << open_Z0 << "\n" << open_delay << "\n" << open_loss << "\n" << open_C0 << "\n" << open_C1 << "\n" << open_C2 << "\n" << open_C3 << "\n";
file << short_Z0 << "\n" << short_delay << "\n" << short_loss << "\n" << short_L0 << "\n" << short_L1 << "\n" << short_L2 << "\n" << short_L3 << "\n";
file << load_Z0 << "\n";
file << through_Z0 << "\n" << through_delay << "\n" << through_loss << "\n";
if(open_measurements) {
file << open_file << "\n" << open_Sparam << "\n";
}
if(short_measurements) {
file << short_file << "\n" << short_Sparam << "\n";
}
if(load_measurements) {
file << load_file << "\n" << load_Sparam << "\n";
}
if(through_measurements) {
file << through_file << "\n" << through_Sparam1 << "\n" << through_Sparam2 << "\n";
}
file.close();
}
Calkit Calkit::fromFile(std::string filename)
{
Calkit c;
ifstream file;
file.open(filename);
if(!file.is_open()) {
throw runtime_error("Unable to open file");
}
file >> c.open_measurements;
file >> c.short_measurements;
file >> c.load_measurements;
file >> c.through_measurements;
file >> c.open_Z0;
file >> c.open_delay;
file >> c.open_loss;
file >> c.open_C0;
file >> c.open_C1;
file >> c.open_C2;
file >> c.open_C3;
file >> c.short_Z0;
file >> c.short_delay;
file >> c.short_loss;
file >> c.short_L0;
file >> c.short_L1;
file >> c.short_L2;
file >> c.short_L3;
file >> c.load_Z0;
file >> c.through_Z0;
file >> c.through_delay;
file >> c.through_loss;
if(c.open_measurements) {
file >> c.open_file;
file >> c.open_Sparam;
}
if(c.short_measurements) {
file >> c.short_file;
file >> c.short_Sparam;
}
if(c.load_measurements) {
file >> c.load_file;
file >> c.load_Sparam;
}
if(c.through_measurements) {
file >> c.through_file;
file >> c.through_Sparam1;
file >> c.through_Sparam2;
}
file.close();
return c;
}
void Calkit::edit()
{
auto dialog = new CalkitDialog(*this);
dialog->show();
}
Calkit::Reflection Calkit::toReflection(double frequency)
{
fillTouchstoneCache();
Reflection ref;
if(load_measurements) {
ref.Load = ts_load->interpolate(frequency).S[0];
} else {
auto imp_load = complex<double>(load_Z0, 0);
ref.Load = (imp_load - complex<double>(50.0)) / (imp_load + complex<double>(50.0));
}
if(open_measurements) {
ref.Open = ts_open->interpolate(frequency).S[0];
} else {
// calculate fringing capacitance for open
double Cfringing = open_C0 * 1e-15 + open_C1 * 1e-27 * frequency + open_C2 * 1e-36 * pow(frequency, 2) + open_C3 * 1e-45 * pow(frequency, 3);
// convert to impedance
if (Cfringing == 0) {
// special case to avoid issues with infinity
ref.Open = complex<double>(1.0, 0);
} else {
auto imp_open = complex<double>(0, -1.0 / (frequency * 2 * M_PI * Cfringing));
ref.Open = (imp_open - complex<double>(50.0)) / (imp_open + complex<double>(50.0));
}
// transform the delay into a phase shift for the given frequency
double open_phaseshift = -2 * M_PI * frequency * open_delay * 1e-12;
double open_att_db = open_loss * 1e9 * 4.3429 * open_delay * 1e-12 / open_Z0 * sqrt(frequency / 1e9);
double open_att = pow(10.0, -open_att_db / 10.0);
auto open_correction = polar<double>(open_att, open_phaseshift);
ref.Open *= open_correction;
}
if(short_measurements) {
ref.Short = ts_short->interpolate(frequency).S[0];
} else {
// calculate inductance for short
double Lseries = short_L0 * 1e-12 + short_L1 * 1e-24 * frequency + short_L2 * 1e-33 * pow(frequency, 2) + short_L3 * 1e-42 * pow(frequency, 3);
// convert to impedance
auto imp_short = complex<double>(0, frequency * 2 * M_PI * Lseries);
ref.Short = (imp_short - complex<double>(50.0)) / (imp_short + complex<double>(50.0));
// transform the delay into a phase shift for the given frequency
double short_phaseshift = -2 * M_PI * frequency * short_delay * 1e-12;
double short_att_db = short_loss * 1e9 * 4.3429 * short_delay * 1e-12 / short_Z0 * sqrt(frequency / 1e9);;
double short_att = pow(10.0, -short_att_db / 10.0);
auto short_correction = polar<double>(short_att, short_phaseshift);
ref.Short *= short_correction;
}
if(through_measurements) {
auto interp = ts_through->interpolate(frequency);
ref.ThroughS11 = interp.S[0];
ref.ThroughS12 = interp.S[1];
ref.ThroughS21 = interp.S[2];
ref.ThroughS22 = interp.S[3];
} else {
// calculate effect of through
double through_phaseshift = -2 * M_PI * frequency * through_delay * 1e-12;
double through_att_db = through_loss * 1e9 * 4.3429 * through_delay * 1e-12 / through_Z0 * sqrt(frequency / 1e9);;
double through_att = pow(10.0, -through_att_db / 10.0);
ref.ThroughS12 = polar<double>(through_att, through_phaseshift);
// Assume symmetric and perfectly matched through for other parameters
ref.ThroughS21 = ref.ThroughS12;
ref.ThroughS11 = 0.0;
ref.ThroughS22 = 0.0;
}
return ref;
}
double Calkit::minFreq()
{
fillTouchstoneCache();
double min = std::numeric_limits<double>::min();
array<Touchstone*, 4> ts_list = {ts_open, ts_short, ts_load, ts_through};
// find the highest minimum frequency in all measurement files
for(auto ts : ts_list) {
if(!ts) {
// this calibration standard is defined by coefficients, no minimum frequency
continue;
}
if(ts->minFreq() > min) {
min = ts->minFreq();
}
}
return min;
}
double Calkit::maxFreq()
{
fillTouchstoneCache();
double max = std::numeric_limits<double>::max();
array<Touchstone*, 4> ts_list = {ts_open, ts_short, ts_load, ts_through};
// find the highest minimum frequency in all measurement files
for(auto ts : ts_list) {
if(!ts) {
// this calibration standard is defined by coefficients, no minimum frequency
continue;
}
if(ts->maxFreq() < max) {
max = ts->maxFreq();
}
}
return max;
}
void Calkit::clearTouchstoneCache()
{
if(ts_open) {
delete ts_open;
ts_open = nullptr;
}
if(ts_short) {
delete ts_short;
ts_short = nullptr;
}
if(ts_load) {
delete ts_load;
ts_load = nullptr;
}
if(ts_through) {
delete ts_through;
ts_through = nullptr;
}
ts_cached = false;
}
void Calkit::fillTouchstoneCache()
{
if(ts_cached) {
return;
}
if(open_measurements) {
ts_open = new Touchstone(1);
*ts_open = Touchstone::fromFile(open_file);
ts_open->reduceTo1Port(open_Sparam);
}
if(short_measurements) {
ts_short = new Touchstone(1);
*ts_short = Touchstone::fromFile(short_file);
ts_open->reduceTo1Port(short_Sparam);
}
if(load_measurements) {
ts_load = new Touchstone(1);
*ts_load = Touchstone::fromFile(load_file);
ts_open->reduceTo1Port(load_Sparam);
}
if(through_measurements) {
ts_through = new Touchstone(2);
*ts_through = Touchstone::fromFile(through_file);
ts_through->reduceTo2Port(through_Sparam1, through_Sparam2);
}
ts_cached = true;
}