WIP: TDR/DFT improvements

Software/PC_Application/LibreVNA-GUI/Traces/Math/dft.cpp

@@ -17,6 +17,8 @@ using namespace std;
 Math::DFT::DFT()
 {
     automaticDC = true;
+    removePaddingFromTDR = true;
+    revertWindowFromTDR = true;
     DCfreq = 1000000000.0;
 
     destructing = false;
@@ -67,12 +69,23 @@ void Math::DFT::edit()
     ui->windowBox->setLayout(new QVBoxLayout);
     ui->windowBox->layout()->addWidget(window.createEditor());
 
-    connect(ui->DCautomatic, &QRadioButton::toggled, [=](bool automatic){
+    connect(ui->removePadding, &QCheckBox::toggled, this, [=](bool remove){
+        removePaddingFromTDR = remove;
+    });
+
+    connect(ui->revertWindow, &QCheckBox::toggled, this, [=](bool revert){
+        revertWindowFromTDR = revert;
+    });
+
+    connect(ui->DCautomatic, &QRadioButton::toggled, this, [=](bool automatic){
         automaticDC = automatic;
         ui->freq->setEnabled(!automatic);
         updateDFT();
     });
 
+    ui->removePadding->setChecked(removePaddingFromTDR);
+    ui->revertWindow->setChecked(revertWindowFromTDR);
+
     if(automaticDC) {
         ui->DCautomatic->setChecked(true);
     } else {
@@ -84,7 +97,7 @@ void Math::DFT::edit()
     ui->freq->setPrefixes(" kMG");
     ui->freq->setValue(DCfreq);
 
-    connect(ui->freq, &SIUnitEdit::valueChanged, [=](double newval){
+    connect(ui->freq, &SIUnitEdit::valueChanged, this, [=](double newval){
         DCfreq = newval;
         updateDFT();
     });
@@ -111,6 +124,8 @@ nlohmann::json Math::DFT::toJSON()
     nlohmann::json j;
     j["automatic_DC"] = automaticDC;
     j["window"] = window.toJSON();
+    j["removePadding"] = removePaddingFromTDR;
+    j["revertWindow"] = revertWindowFromTDR;
     if(!automaticDC) {
         j["DC"] = DCfreq;
     }
@@ -124,6 +139,8 @@ void Math::DFT::fromJSON(nlohmann::json j)
     if(j.contains("window")) {
         window.fromJSON(j["window"]);
     }
+    removePaddingFromTDR = j.value("removePadding", true);
+    revertWindowFromTDR = j.value("revertWindow", true);
 }
 
 void Math::DFT::inputSamplesChanged(unsigned int begin, unsigned int end)
@@ -169,38 +186,33 @@ void Math::DFTThread::run()
             qDebug() << "DFT thread exiting";
             return;
         }
-        // limit update rate if configured in preferences
-        auto &p = Preferences::getInstance();
-        if(p.Acquisition.limitDFT) {
-            std::this_thread::sleep_until(lastCalc + duration<double>(1.0 / p.Acquisition.maxDFTrate));
-            lastCalc = system_clock::now();
-        }
 //        qDebug() << "DFT thread calculating";
+        if(!dft.input) {
+            // not connected, skip calculation
+            continue;
+        }
         double DC = dft.DCfreq;
         TDR *tdr = nullptr;
-        if(dft.automaticDC) {
+        // find the last TDR operation
-            // find the last operation that transformed from the frequency domain to the time domain
+        auto in = dft.input;
-            auto in = dft.input;
+        while(in->getType() != DFT::Type::TDR) {
-            while(in->getInput()->getDataType() != DFT::DataType::Frequency) {
+            in = dft.input->getInput();
-                in = dft.input->getInput();
+            if(!in) {
-            }
-            switch(in->getType()) {
-            case DFT::Type::TDR: {
-                tdr = static_cast<TDR*>(in);
-                if(tdr->getMode() == TDR::Mode::Lowpass) {
-                    DC = 0;
-                } else {
-                    // bandpass mode, assume DC is in the middle of the frequency data
-                    DC = tdr->getInput()->getSample(tdr->getInput()->numSamples()/2).x;
-                }
-            }
-                break;
-            default:
-                // unknown, assume DC is in the middle of the frequency data
-                DC = in->getInput()->getSample(in->getInput()->numSamples()/2).x;
                 break;
             }
         }
+        if(in) {
+            tdr = static_cast<TDR*>(in);
+        }
+
+        if(tdr && dft.automaticDC) {
+            if(tdr->getMode() == TDR::Mode::Lowpass) {
+                DC = 0;
+            } else {
+                // bandpass mode, assume DC is in the middle of the frequency data
+                DC = tdr->getInput()->getSample(tdr->getInput()->numSamples()/2).x;
+            }
+        }
         auto samples = dft.input->rData().size();
         auto timeSpacing = dft.input->rData()[1].x - dft.input->rData()[0].x;
         vector<complex<double>> timeDomain(samples);
@@ -208,14 +220,34 @@ void Math::DFTThread::run()
             timeDomain.at(i) = dft.input->rData()[i].y;
         }
 
-        Fft::shift(timeDomain, false);
         dft.window.apply(timeDomain);
-        Fft::shift(timeDomain, true);
         Fft::transform(timeDomain, false);
         // shift DC bin into the middle
         Fft::shift(timeDomain, false);
 
         double binSpacing = 1.0 / (timeSpacing * timeDomain.size());
+
+        if(tdr) {
+            // split in padding and actual data sections
+            unsigned int padding = timeDomain.size() - tdr->getUnpaddedInputSize();
+            std::vector<std::complex<double>> pad_front(timeDomain.begin(), timeDomain.begin()+padding/2);
+            std::vector<std::complex<double>> data(timeDomain.begin()+padding/2, timeDomain.end()-padding/2);
+            std::vector<std::complex<double>> pad_back(timeDomain.end()-padding/2, timeDomain.end());
+
+            if(dft.revertWindowFromTDR) {
+                tdr->getWindow().reverse(data);
+            }
+
+            if(dft.removePaddingFromTDR) {
+                timeDomain = data;
+            } else {
+                // include padding
+                timeDomain = pad_front;
+                copy(data.begin(), data.end(), back_inserter(timeDomain));
+                copy(pad_back.begin(), pad_back.end(), back_inserter(timeDomain));
+            }
+        }
+
         dft.data.clear();
         int DCbin = timeDomain.size() / 2, startBin = 0;
         if(DC > 0) {
@@ -225,16 +257,18 @@ void Math::DFTThread::run()
             dft.data.resize(timeDomain.size()/2, TraceMath::Data());
         }
 
-        // reverse effect of frequency domain window function from TDR (if available)
-        if(tdr) {
-            tdr->getWindow().reverse(timeDomain);
-        }
-
         for(int i = startBin;(unsigned int) i<timeDomain.size();i++) {
             auto freq = (i - DCbin) * binSpacing + DC;
             dft.data[i - startBin].x = round(freq);
             dft.data[i - startBin].y = timeDomain.at(i);
         }
         emit dft.outputSamplesChanged(0, dft.data.size());
+
+        // limit update rate if configured in preferences
+        auto &p = Preferences::getInstance();
+        if(p.Acquisition.limitDFT) {
+            std::this_thread::sleep_until(lastCalc + duration<double>(1.0 / p.Acquisition.maxDFTrate));
+            lastCalc = system_clock::now();
+        }
     }
 }

Software/PC_Application/LibreVNA-GUI/Traces/Math/dft.h

@@ -48,6 +48,8 @@ private:
     bool automaticDC;
     double DCfreq;
     WindowFunction window;
+    bool removePaddingFromTDR;
+    bool revertWindowFromTDR;
     DFTThread *thread;
     bool destructing;
     QSemaphore semphr;

Software/PC_Application/LibreVNA-GUI/Traces/Math/dftdialog.ui

@@ -3,7 +3,7 @@
  <class>DFTDialog</class>
  <widget class="QDialog" name="DFTDialog">
   <property name="windowModality">
-   <enum>Qt::ApplicationModal</enum>
+   <enum>Qt::WindowModality::ApplicationModal</enum>
   </property>
   <property name="geometry">
    <rect>
@@ -19,7 +19,21 @@
   <property name="modal">
    <bool>true</bool>
   </property>
-  <layout class="QVBoxLayout" name="verticalLayout" stretch="0,1,0">
+  <layout class="QVBoxLayout" name="verticalLayout" stretch="0,0,0,1,0">
+   <item>
+    <widget class="QCheckBox" name="removePadding">
+     <property name="text">
+      <string>Remove possible padding from last TDR</string>
+     </property>
+    </widget>
+   </item>
+   <item>
+    <widget class="QCheckBox" name="revertWindow">
+     <property name="text">
+      <string>Revert window function from last TDR</string>
+     </property>
+    </widget>
+   </item>
    <item>
     <widget class="QGroupBox" name="groupBox">
      <property name="title">
@@ -83,7 +97,7 @@
    <item>
     <widget class="QDialogButtonBox" name="buttonBox">
      <property name="standardButtons">
-      <set>QDialogButtonBox::Ok</set>
+      <set>QDialogButtonBox::StandardButton::Ok</set>
      </property>
     </widget>
    </item>

Software/PC_Application/LibreVNA-GUI/Traces/Math/tdr.cpp

@@ -22,6 +22,7 @@ TDR::TDR()
     manualDC = 1.0;
     stepResponse = true;
     mode = Mode::Lowpass;
+    padding = 0;
 
     destructing = false;
     thread = new TDRThread(*this);
@@ -86,19 +87,23 @@ void TDR::edit()
         ui->manualMag->setEnabled(enable);
     };
 
-    connect(ui->mode, qOverload<int>(&QComboBox::currentIndexChanged), [=](int index){
+    connect(ui->mode, qOverload<int>(&QComboBox::currentIndexChanged), this, [=](int index){
         mode = (Mode) index;
         updateEnabledWidgets();
         updateTDR();
     });
 
-    connect(ui->computeStepResponse, &QCheckBox::toggled, [=](bool computeStep) {
+    connect(ui->padding, &QSpinBox::valueChanged, this, [=](int value) {
+        padding = value;
+    });
+
+    connect(ui->computeStepResponse, &QCheckBox::toggled, this, [=](bool computeStep) {
        stepResponse = computeStep;
         updateEnabledWidgets();
        updateTDR();
     });
 
-    connect(ui->DCmanual, &QRadioButton::toggled, [=](bool manual) {
+    connect(ui->DCmanual, &QRadioButton::toggled, this, [=](bool manual) {
         automaticDC = !manual;
         updateEnabledWidgets();
         updateTDR();
@@ -114,6 +119,8 @@ void TDR::edit()
         ui->mode->setCurrentIndex(1);
     }
 
+    ui->padding->setValue(padding);
+
     ui->manualMag->setUnit("dBm");
     ui->manualMag->setPrecision(3);
     ui->manualMag->setValue(Util::SparamTodB(manualDC));
@@ -121,11 +128,11 @@ void TDR::edit()
     ui->manualPhase->setPrecision(4);
     ui->manualPhase->setValue(180.0/M_PI * arg(manualDC));
 
-    connect(ui->manualMag, &SIUnitEdit::valueChanged, [=](double newval){
+    connect(ui->manualMag, &SIUnitEdit::valueChanged, this, [=](double newval){
         manualDC = polar(pow(10, newval / 20.0), arg(manualDC));
         updateTDR();
     });
-    connect(ui->manualPhase, &SIUnitEdit::valueChanged, [=](double newval){
+    connect(ui->manualPhase, &SIUnitEdit::valueChanged, this, [=](double newval){
         manualDC = polar(abs(manualDC), newval * M_PI / 180.0);
         updateTDR();
     });
@@ -152,6 +159,7 @@ nlohmann::json TDR::toJSON()
     nlohmann::json j;
     j["bandpass_mode"] = mode == Mode::Bandpass;
     j["window"] = window.toJSON();
+    j["padding"] = padding;
     if(mode == Mode::Lowpass) {
         j["step_response"] = stepResponse;
         if(stepResponse) {
@@ -170,6 +178,7 @@ void TDR::fromJSON(nlohmann::json j)
     if(j.contains("window")) {
         window.fromJSON(j["window"]);
     }
+    padding = j.value("padding", 0);
     if(j.value("bandpass_mode", true)) {
         mode = Mode::Bandpass;
     } else {
@@ -224,6 +233,11 @@ void TDR::updateTDR()
     }
 }
 
+unsigned int TDR::getUnpaddedInputSize() const
+{
+    return unpaddedInputSize;
+}
+
 const WindowFunction& TDR::getWindow() const
 {
     return window;
@@ -254,14 +268,12 @@ void TDRThread::run()
             qDebug() << "TDR thread exiting";
             return;
         }
-        // limit update rate if configured in preferences
-        auto &p = Preferences::getInstance();
-        if(p.Acquisition.limitDFT) {
-            std::this_thread::sleep_until(lastCalc + duration<double>(1.0 / p.Acquisition.maxDFTrate));
-            lastCalc = system_clock::now();
-        }
 //        qDebug() << "TDR thread calculating";
         // perform calculation
+        if(!tdr.input) {
+            // not connected, skip calculation
+            continue;
+        }
         vector<complex<double>> frequencyDomain;
         auto stepSize = (tdr.input->rData().back().x - tdr.input->rData().front().x) / (tdr.input->rData().size() - 1);
         if(tdr.mode == TDR::Mode::Lowpass) {
@@ -321,6 +333,12 @@ void TDRThread::run()
         }
 
         tdr.window.apply(frequencyDomain);
+        tdr.unpaddedInputSize = frequencyDomain.size();
+        if(frequencyDomain.size() < tdr.padding) {
+            auto missing = tdr.padding - frequencyDomain.size();
+            frequencyDomain.insert(frequencyDomain.begin(), missing/2, 0);
+            frequencyDomain.insert(frequencyDomain.end(), missing/2, 0);
+        }
         Fft::shift(frequencyDomain, true);
 
         int fft_bins = frequencyDomain.size();
@@ -341,5 +359,12 @@ void TDRThread::run()
             tdr.updateStepResponse(false);
         }
         emit tdr.outputSamplesChanged(0, tdr.data.size());
+
+        // limit update rate if configured in preferences
+        auto &p = Preferences::getInstance();
+        if(p.Acquisition.limitDFT) {
+            std::this_thread::sleep_until(lastCalc + duration<double>(1.0 / p.Acquisition.maxDFTrate));
+            lastCalc = system_clock::now();
+        }
     }
 }

Software/PC_Application/LibreVNA-GUI/Traces/Math/tdr.h

@@ -48,6 +48,8 @@ public:
     Mode getMode() const;
     const WindowFunction& getWindow() const;
 
+    unsigned int getUnpaddedInputSize() const;
+
 public slots:
     void inputSamplesChanged(unsigned int begin, unsigned int end) override;
 
@@ -55,6 +57,8 @@ private:
     void updateTDR();
     Mode mode;
     WindowFunction window;
+    unsigned int padding;
+    unsigned int unpaddedInputSize;
     bool stepResponse;
     bool automaticDC;
     std::complex<double> manualDC;

Software/PC_Application/LibreVNA-GUI/Traces/Math/tdrdialog.ui

@@ -3,7 +3,7 @@
  <class>TDRDialog</class>
  <widget class="QDialog" name="TDRDialog">
   <property name="windowModality">
-   <enum>Qt::ApplicationModal</enum>
+   <enum>Qt::WindowModality::ApplicationModal</enum>
   </property>
   <property name="geometry">
    <rect>
@@ -43,6 +43,23 @@
        </item>
       </widget>
      </item>
+     <item row="1" column="0">
+      <widget class="QLabel" name="label_4">
+       <property name="text">
+        <string>Padding:</string>
+       </property>
+      </widget>
+     </item>
+     <item row="1" column="1">
+      <widget class="QSpinBox" name="padding">
+       <property name="maximum">
+        <number>100000</number>
+       </property>
+       <property name="singleStep">
+        <number>100</number>
+       </property>
+      </widget>
+     </item>
     </layout>
    </item>
    <item>
@@ -129,7 +146,7 @@
    <item>
     <widget class="QDialogButtonBox" name="buttonBox">
      <property name="standardButtons">
-      <set>QDialogButtonBox::Ok</set>
+      <set>QDialogButtonBox::StandardButton::Ok</set>
      </property>
     </widget>
    </item>