Added SCPI command for touchstone file format

Documentation/UserManual/ProgrammingGuide.tex

@@ -422,6 +422,30 @@ Depending on the sweep and possible confiigured math operations, x may be either
 -0.0458452,-0.028729
 \end{example}
 
+\subsubsection{VNA:TRACe:TOUCHSTONE}
+\query{Returns the content of multiple trace according to the touchstone format}{VNA:TRACe:TOUCHSTONE?}{<trace1>,<trace2>,<trace3>,...}{Touchstone file content in ASCII}
+Some additional constraints apply:
+\begin{itemize}
+\item The number of specified traces must be a square number. The number of ports in the touchstone file is inferred from that.
+\item Only frequency domain traces are allowed.
+\item All traces must have the same number of points and the same start/stop frequency.
+\item The order in which the traces are specified matters and depending on its index and each trace must be a reflection or transmission measurement:
+\begin{itemize}
+\item Assuming that $n$ is the number of ports of the desired touchstone file, the $n*n$ number of traces must be specified in this order:
+$$ S_{11}...S_{1n},S_{21}...S_{2n},...,S_{n1}...S_{nn} $$
+\item For every trace $S_{ij}$, the trace must contain a reflection measurement if $i=j$ and a transmission measurement if $i\neq j$.
+\end{itemize}
+\item Traces can be specified either by name or by index.
+\item A deviation from any of these points (invalid number of traces, non-existing trace, wrong order, ...) will result in an error being returned.
+\end{itemize}
+\begin{example}
+:VNA:TRACE:TOUCHSTONE? S11 S12 S21 S22
+# GHZ S RI R 50
+1.000000000000 1.000497817993 0.010679213330 0.000013886895 -0.000054684886 -0.000023392624 -0.000021111371 0.401717424393 0.702864229679
+1.002000000000 1.000323534012 0.010577851906 -0.000011075452 -0.000013504875 0.000000477609 -0.000007789199 0.413144201040 0.696514129639
+...
+\end{example}
+
 \subsubsection{VNA:TRACe:MAXFrequency}
 \query{Returns the highest frequency contained in the trace}{VNA:TRACe:MAXFrequency?}{<trace>, either by name or by index}{maximum frequency in Hz}
 

Software/PC_Application/Traces/tracewidget.cpp

@@ -141,13 +141,10 @@ void TraceWidget::on_view_clicked(const QModelIndex &index)
 
 void TraceWidget::SetupSCPI()
 {
-    auto findTrace = [=](QStringList params) -> Trace* {
+    auto findTraceFromName = [=](QString name) -> Trace* {
-        if(params.size() < 1) {
-            return nullptr;
-        }
         // check if trace is specified by number
         bool ok;
-        auto n = params[0].toUInt(&ok);
+        auto n = name.toUInt(&ok);
         if(ok) {
             // check if enough traces exist
             if(n < model.getTraces().size()) {
@@ -159,7 +156,7 @@ void TraceWidget::SetupSCPI()
         } else {
             // trace specified by name
             for(auto t : model.getTraces()) {
-                if(t->name().compare(params[0], Qt::CaseInsensitive) == 0) {
+                if(t->name().compare(name, Qt::CaseInsensitive) == 0) {
                     return t;
                 }
             }
@@ -167,6 +164,12 @@ void TraceWidget::SetupSCPI()
             return nullptr;
         }
     };
+    auto findTrace = [=](QStringList params) -> Trace* {
+        if(params.size() < 1) {
+            return nullptr;
+        }
+        return findTraceFromName(params[0]);
+    };
 
     auto createStringFromData = [](Trace *t, const Trace::Data &d) -> QString {
         if(Trace::isSAParamater(t->liveParameter())) {
@@ -220,6 +223,63 @@ void TraceWidget::SetupSCPI()
             }
         }
     }));
+    add(new SCPICommand("TOUCHSTONE", nullptr, [=](QStringList params) -> QString {
+        if(params.size() < 1) {
+            // no traces given
+            return "ERROR";
+        }
+        // check number of paramaters, must be a square number
+        int numTraces = params.size();
+        int ports = round(sqrt(numTraces));
+        if(ports * ports != numTraces) {
+            // invalid number of traces
+            return "ERROR";
+        }
+        Trace* traces[numTraces];
+        for(int i=0;i<numTraces;i++) {
+            traces[i] = findTraceFromName(params[i]);
+            if(!traces[i]) {
+                // couldn't find that trace
+                return "ERROR";
+            }
+        }
+        // check if trace selection is valid
+        auto npoints = traces[0]->size();
+        auto f_start = traces[0]->minX();
+        auto f_stop = traces[0]->maxX();
+        for(int i=0;i<ports;i++) {
+            for(int j=0;j<ports;j++) {
+                bool need_reflection = i==j;
+                auto t = traces[j+i*ports];
+                if(t->getDataType() != Trace::DataType::Frequency) {
+                    // invalid domain
+                    return "ERROR";
+                }
+                if(t->isReflection() != need_reflection) {
+                    // invalid measurement at this position
+                    return "ERROR";
+                }
+                if((t->size() != npoints) || (t->minX() != f_start) || (t->maxX() != f_stop)) {
+                    // frequency points are not identical
+                    return "ERROR";
+                }
+            }
+        }
+        // all traces checked, they are valid.
+        // Constructing touchstone
+        Touchstone t = Touchstone(ports);
+        for(unsigned int i=0;i<npoints;i++) {
+            Touchstone::Datapoint d;
+            d.frequency = traces[0]->getSample(i).x;
+            for(auto trace : traces) {
+                d.S.push_back(trace->getSample(i).y);
+            }
+            t.AddDatapoint(d);
+        }
+        // touchstone assembled, save to dummyfile
+        auto s = t.toString(Touchstone::Scale::GHz, Touchstone::Format::RealImaginary);
+        return QString::fromStdString(s.str());
+    }));
     add(new SCPICommand("MAXFrequency", nullptr, [=](QStringList params) -> QString {
         auto t = findTrace(params);
         if(!t) {

Software/PC_Application/touchstone.cpp

@@ -7,6 +7,7 @@
 #include <cctype>
 #include <string>
 #include "Util/util.h"
+#include <QDebug>
 
 using namespace std;
 
@@ -45,25 +46,34 @@ void Touchstone::toFile(string filename, Scale unit, Format format)
     // create file
     ofstream file;
     file.open(filename);
-    file << std::fixed << std::setprecision(12);
 
+    file << toString(unit, format).rdbuf();
+
+    file.close();
+    this->filename = QString::fromStdString(filename);
+}
+
+stringstream Touchstone::toString(Touchstone::Scale unit, Touchstone::Format format)
+{
+    stringstream s;
+    s << std::fixed << std::setprecision(12);
     // write option line
-    file << "# ";
+    s << "# ";
     switch(unit) {
-        case Scale::Hz: file << "HZ "; break;
+        case Scale::Hz: s << "HZ "; break;
-        case Scale::kHz: file << "KHZ "; break;
+        case Scale::kHz: s << "KHZ "; break;
-        case Scale::MHz: file << "MHZ "; break;
+        case Scale::MHz: s << "MHZ "; break;
-        case Scale::GHz: file << "GHZ "; break;
+        case Scale::GHz: s << "GHZ "; break;
     }
     // only S parameters supported so far
-    file << "S ";
+    s << "S ";
     switch(format) {
-        case Format::DBAngle: file << "DB "; break;
+        case Format::DBAngle: s << "DB "; break;
-        case Format::RealImaginary: file << "RI "; break;
+        case Format::RealImaginary: s << "RI "; break;
-        case Format::MagnitudeAngle: file << "MA "; break;
+        case Format::MagnitudeAngle: s << "MA "; break;
     }
     // reference impedance is always 50 ohm
-    file << "R 50\n";
+    s << "R 50\n";
 
     auto printParameter = [format](ostream &out, complex<double> &c) {
         switch (format) {
@@ -81,45 +91,44 @@ void Touchstone::toFile(string filename, Scale unit, Format format)
 
     for(auto p : m_datapoints) {
         switch(unit) {
-            case Scale::Hz: file << p.frequency; break;
+            case Scale::Hz: s << p.frequency; break;
-            case Scale::kHz: file << p.frequency / 1e3; break;
+            case Scale::kHz: s << p.frequency / 1e3; break;
-            case Scale::MHz: file << p.frequency / 1e6; break;
+            case Scale::MHz: s << p.frequency / 1e6; break;
-            case Scale::GHz: file << p.frequency / 1e9; break;
+            case Scale::GHz: s << p.frequency / 1e9; break;
         }
-        file << " ";
+        s << " ";
         // special cases for 1 and 2 port
         if (m_ports == 1) {
-            printParameter(file, p.S[0]);
+            printParameter(s, p.S[0]);
-            file << "\n";
+            s << "\n";
         } else if (m_ports == 2){
-            printParameter(file, p.S[0]);
+            printParameter(s, p.S[0]);
             // touchstone expects S11 S21 S12 S22 order, swap S12 and S21
-            file << " ";
+            s << " ";
-            printParameter(file, p.S[2]);
+            printParameter(s, p.S[2]);
-            file << " ";
+            s << " ";
-            printParameter(file, p.S[1]);
+            printParameter(s, p.S[1]);
-            file << " ";
+            s << " ";
-            printParameter(file, p.S[3]);
+            printParameter(s, p.S[3]);
-            file << "\n";
+            s << "\n";
         } else {
             // print parameters in matrix form
             for(unsigned int i=0;i<m_ports;i++) {
                 for(unsigned int j=0;j<m_ports;j++) {
-                    printParameter(file, p.S[i*m_ports + j]);
+                    printParameter(s, p.S[i*m_ports + j]);
                     if (j%4 == 3) {
-                        file << "\n";
+                        s << "\n";
                     } else {
-                        file << " ";
+                        s << " ";
                     }
                 }
                 if(m_ports%4 != 0) {
-                    file << "\n";
+                    s << "\n";
                 }
             }
         }
     }
-    file.close();
+    return s;
-    this->filename = QString::fromStdString(filename);
 }
 
 Touchstone Touchstone::fromFile(string filename)

Software/PC_Application/touchstone.h

@@ -31,6 +31,7 @@ public:
     Touchstone(unsigned int m_ports);
     void AddDatapoint(Datapoint p);
     void toFile(std::string filename, Scale unit = Scale::GHz, Format format = Format::RealImaginary);
+    std::stringstream toString(Scale unit = Scale::GHz, Format format = Format::RealImaginary);
     static Touchstone fromFile(std::string filename);
     double minFreq();
     double maxFreq();