Added measurement graphs showing impedance measured via S21

Fixes #165

- Allows for both |Z| and R + jX display
- Measurements of shunt impedance (accurate for low impedance values)
  as well as series impedance (accurate for high impedance values)

NanoVNASaver/Charts/MagnitudeZ.py

@@ -89,6 +89,8 @@ class MagnitudeZChart(FrequencyChart):
             maxValue = 0
             for d in self.data:
                 mag = self.magnitude(d)
+                if math.isinf(mag): # Avoid infinite scales
+                    continue
                 if mag > maxValue:
                     maxValue = mag
                 if mag < minValue:
@@ -97,6 +99,8 @@ class MagnitudeZChart(FrequencyChart):
                 if d.freq < self.fstart or d.freq > self.fstop:
                     continue
                 mag = self.magnitude(d)
+                if math.isinf(mag): # Avoid infinite scales
+                    continue
                 if mag > maxValue:
                     maxValue = mag
                 if mag < minValue:
@@ -142,7 +146,10 @@ class MagnitudeZChart(FrequencyChart):
 
     def getYPosition(self, d: Datapoint) -> int:
         mag = self.magnitude(d)
-        return self.topMargin + round((self.maxValue - mag) / self.span * self.chartHeight)
+        if math.isfinite(mag):
+            return self.topMargin + round((self.maxValue - mag) / self.span * self.chartHeight)
+        else:
+            return self.topMargin
 
     def valueAtPosition(self, y) -> List[float]:
         absy = y - self.topMargin

NanoVNASaver/Charts/MagnitudeZSeries.py

@@ -0,0 +1,40 @@
+
+#  NanoVNASaver
+#
+#  A python program to view and export Touchstone data from a NanoVNA
+#  Copyright (C) 2019, 2020  Rune B. Broberg
+#  Copyright (C) 2020 NanoVNA-Saver Authors
+#
+#  This program is free software: you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation, either version 3 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+import math
+import logging
+from typing import List
+
+from PyQt5 import QtWidgets, QtGui
+
+from NanoVNASaver.RFTools import Datapoint
+from .MagnitudeZ import MagnitudeZChart
+
+
+logger = logging.getLogger(__name__)
+
+
+class MagnitudeZSeriesChart(MagnitudeZChart):
+    def __init__(self, name=""):
+        super().__init__(name)
+
+    @staticmethod
+    def magnitude(p: Datapoint) -> float:
+        return abs(p.seriesImpedance())
+

NanoVNASaver/Charts/MagnitudeZShunt.py

@@ -0,0 +1,40 @@
+
+#  NanoVNASaver
+#
+#  A python program to view and export Touchstone data from a NanoVNA
+#  Copyright (C) 2019, 2020  Rune B. Broberg
+#  Copyright (C) 2020 NanoVNA-Saver Authors
+#
+#  This program is free software: you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation, either version 3 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+import math
+import logging
+from typing import List
+
+from PyQt5 import QtWidgets, QtGui
+
+from NanoVNASaver.RFTools import Datapoint
+from .MagnitudeZ import MagnitudeZChart
+
+
+logger = logging.getLogger(__name__)
+
+
+class MagnitudeZShuntChart(MagnitudeZChart):
+    def __init__(self, name=""):
+        super().__init__(name)
+
+    @staticmethod
+    def magnitude(p: Datapoint) -> float:
+        return abs(p.shuntImpedance())
+

NanoVNASaver/Charts/RI.py

@@ -178,8 +178,10 @@ class RealImaginaryChart(FrequencyChart):
             max_real = 0
             max_imag = -1000
             for d in self.data:
-                imp = d.impedance()
+                imp = self.impedance(d)
                 re, im = imp.real, imp.imag
+                if math.isinf(re): # Avoid infinite scales
+                    continue
                 if re > max_real:
                     max_real = re
                 if re < min_real:
@@ -191,8 +193,10 @@ class RealImaginaryChart(FrequencyChart):
             for d in self.reference:  # Also check min/max for the reference sweep
                 if d.freq < fstart or d.freq > fstop:
                     continue
-                imp = d.impedance()
+                imp = self.impedance(d)
                 re, im = imp.real, imp.imag
+                if math.isinf(re): # Avoid infinite scales
+                    continue
                 if re > max_real:
                     max_real = re
                 if re < min_real:
@@ -397,12 +401,15 @@ class RealImaginaryChart(FrequencyChart):
                 self.drawMarker(x, y_im, qp, m.color, self.markers.index(m)+1)
 
     def getImYPosition(self, d: Datapoint) -> int:
-        im = d.impedance().imag
+        im = self.impedance(d).imag
         return self.topMargin + round((self.max_imag - im) / self.span_imag * self.chartHeight)
 
     def getReYPosition(self, d: Datapoint) -> int:
-        re = d.impedance().real
-        return self.topMargin + round((self.max_real - re) / self.span_real * self.chartHeight)
+        re = self.impedance(d).real
+        if math.isfinite(re):
+            return self.topMargin + round((self.max_real - re) / self.span_real * self.chartHeight)
+        else:
+            return self.topMargin
 
     def valueAtPosition(self, y) -> List[float]:
         absy = y - self.topMargin
@@ -520,3 +527,6 @@ class RealImaginaryChart(FrequencyChart):
         self.action_set_fixed_maximum_imag.setText(
             f"Maximum jX ({self.maxDisplayImag})")
         self.menu.exec_(event.globalPos())
+
+    def impedance(self, p: Datapoint) -> complex:
+        return p.impedance()

NanoVNASaver/Charts/RISeries.py

@@ -0,0 +1,35 @@
+#  NanoVNASaver
+#
+#  A python program to view and export Touchstone data from a NanoVNA
+#  Copyright (C) 2019, 2020  Rune B. Broberg
+#  Copyright (C) 2020 NanoVNA-Saver Authors
+#
+#  This program is free software: you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation, either version 3 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+import math
+import logging
+from typing import List
+
+from NanoVNASaver.RFTools import Datapoint
+
+from .RI import RealImaginaryChart
+
+logger = logging.getLogger(__name__)
+
+
+class RealImaginarySeriesChart(RealImaginaryChart):
+    def __init__(self, name=""):
+        super().__init__(name)
+
+    def impedance(self, p: Datapoint) -> complex:
+        return p.seriesImpedance()

NanoVNASaver/Charts/RIShunt.py

@@ -0,0 +1,35 @@
+#  NanoVNASaver
+#
+#  A python program to view and export Touchstone data from a NanoVNA
+#  Copyright (C) 2019, 2020  Rune B. Broberg
+#  Copyright (C) 2020 NanoVNA-Saver Authors
+#
+#  This program is free software: you can redistribute it and/or modify
+#  it under the terms of the GNU General Public License as published by
+#  the Free Software Foundation, either version 3 of the License, or
+#  (at your option) any later version.
+#
+#  This program is distributed in the hope that it will be useful,
+#  but WITHOUT ANY WARRANTY; without even the implied warranty of
+#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#  GNU General Public License for more details.
+#
+#  You should have received a copy of the GNU General Public License
+#  along with this program.  If not, see <https://www.gnu.org/licenses/>.
+import math
+import logging
+from typing import List
+
+from NanoVNASaver.RFTools import Datapoint
+
+from .RI import RealImaginaryChart
+
+logger = logging.getLogger(__name__)
+
+
+class RealImaginaryShuntChart(RealImaginaryChart):
+    def __init__(self, name=""):
+        super().__init__(name)
+
+    def impedance(self, p: Datapoint) -> complex:
+        return p.shuntImpedance()

NanoVNASaver/Charts/__init__.py

@@ -9,10 +9,14 @@ from .LogMag import LogMagChart
 from .CLogMag import CombinedLogMagChart
 from .Magnitude import MagnitudeChart
 from .MagnitudeZ import MagnitudeZChart
+from .MagnitudeZShunt import MagnitudeZShuntChart
+from .MagnitudeZSeries import MagnitudeZSeriesChart
 from .Permeability import PermeabilityChart
 from .Phase import PhaseChart
 from .QFactor import QualityFactorChart
 from .RI import RealImaginaryChart
+from .RIShunt import RealImaginaryShuntChart
+from .RISeries import RealImaginarySeriesChart
 from .Smith import SmithChart
 from .SParam import SParameterChart
 from .TDR import TDRChart

NanoVNASaver/NanoVNASaver.py

@@ -40,9 +40,9 @@ from .Charts import (
     CapacitanceChart,
     CombinedLogMagChart, GroupDelayChart, InductanceChart,
     LogMagChart, PhaseChart,
-    MagnitudeChart, MagnitudeZChart,
+    MagnitudeChart, MagnitudeZChart, MagnitudeZShuntChart, MagnitudeZSeriesChart,
     QualityFactorChart, VSWRChart, PermeabilityChart, PolarChart,
-    RealImaginaryChart,
+    RealImaginaryChart, RealImaginaryShuntChart, RealImaginarySeriesChart,
     SmithChart, SParameterChart, TDRChart,
 )
 from .Calibration import Calibration
@@ -155,6 +155,10 @@ class NanoVNASaver(QtWidgets.QWidget):
                                                 reflective=False)),
                 ("log_mag", LogMagChart("S21 Gain")),
                 ("magnitude", MagnitudeChart("|S21|")),
+                ("magnitude_z_shunt", MagnitudeZShuntChart("S21 |Z| shunt")),
+                ("magnitude_z_series", MagnitudeZSeriesChart("S21 |Z| series")),
+                ("real_imag_shunt", RealImaginaryShuntChart("S21 R+jX shunt")),
+                ("real_imag_series", RealImaginarySeriesChart("S21 R+jX series")),
                 ("phase", PhaseChart("S21 Phase")),
                 ("polar", PolarChart("S21 Polar Plot")),
                 ("s_parameter", SParameterChart("S21 Real/Imaginary")),

NanoVNASaver/RFTools.py

@@ -67,6 +67,18 @@ class Datapoint(NamedTuple):
     def impedance(self, ref_impedance: float = 50) -> complex:
         return gamma_to_impedance(self.z, ref_impedance)
 
+    def shuntImpedance(self, ref_impedance: float = 50) -> complex:
+        try:
+            return 0.5 * ref_impedance * self.z / (1 - self.z)
+        except ZeroDivisionError:
+            return math.inf
+
+    def seriesImpedance(self, ref_impedance: float = 50) -> complex:
+        try:
+            return 2 * ref_impedance * (1 - self.z) / self.z
+        except ZeroDivisionError:
+            return math.inf
+
     def qFactor(self, ref_impedance: float = 50) -> float:
         imp = self.impedance(ref_impedance)
         if imp.real == 0.0: