Added information on calibration.

src/nqrduck_autotm/controller.py

@@ -121,6 +121,14 @@ class AutoTMController(ModuleController):
     def calculate_calibration(self) -> None:
         """This method is called when the calculate calibration button is pressed.
         It calculates the calibration from the short, open and calibration data points.
+
+        @TODO: Make calibration useful. Right now the calibration does not work for the probe coils. It completly messes up the S11 data.
+        For 50 Ohm reference loads the calibration makes the S11 data usable - one then gets a flat line at -50 dB.
+        The problem is probably two things:
+        1. The ideal values for open, short and load  should be measured with a VNA and then be loaded for the calibration. 
+        The ideal values are probably not -1, 1 and 0 but will also show frequency dependent behaviour.
+        2 The AD8302 chip only returns the absolute value of the phase. One would probably need to calculate the phase with various algorithms found in the literature.
+        Though Im not sure if these proposed algorithms would work for the AD8302 chip.
         """
         logger.debug("Calculating calibration")
         # First we check if the short and open calibration data points are available
@@ -143,26 +151,40 @@ class AutoTMController(ModuleController):
         measured_gamma_open = self.module.model.open_calibration.gamma
         measured_gamma_load = self.module.model.load_calibration.gamma
 
-        e_00s = []
-        e11s = []
-        delta_es = []
+        E_Ds = []
+        E_Ss = []
+        E_ts = []
         for gamma_s, gamma_o, gamma_l in zip(measured_gamma_short, measured_gamma_open, measured_gamma_load):
-            A = np.array([
-                [1, ideal_gamma_short * gamma_s, -ideal_gamma_short],
-                [1, ideal_gamma_open * gamma_o, -ideal_gamma_open],
-                [1, ideal_gamma_load * gamma_l, -ideal_gamma_load]
-            ])
+            # This is the solution from 
+            # A = np.array([
+            #      [1, ideal_gamma_short * gamma_s, -ideal_gamma_short],
+            #      [1, ideal_gamma_open * gamma_o, -ideal_gamma_open],
+            #      [1, ideal_gamma_load * gamma_l, -ideal_gamma_load]
+            #  ])
 
-            B = np.array([gamma_s, gamma_o, gamma_l])
+            # B = np.array([gamma_s, gamma_o, gamma_l])
 
             # Solve the system
-            e_00, e11, delta_e = np.linalg.lstsq(A, B, rcond=None)[0]
+            # e_00, e11, delta_e = np.linalg.lstsq(A, B, rcond=None)[0]
 
-            e_00s.append(e_00)
-            e11s.append(e11)
-            delta_es.append(delta_e)
+            E_D = gamma_l
+            E_ = (2 * gamma_l - (gamma_s  + gamma_o)) / (gamma_s - gamma_o)
+            E_S = (2 * (gamma_o + gamma_l) * (gamma_s + gamma_l)) / (gamma_s - gamma_o)
 
-        self.module.model.calibration = (e_00s, e11s, delta_es)
+            E_Ds.append(E_D)
+            E_Ss.append(E_S)
+            E_ts.append(E_)
+            # e_00 = gamma_l # Because here the reflection coefficient should be 0
+
+            # e11 = (gamma_o + gamma_o - 2 * e_00) / (gamma_o - gamma_s)
+
+            # delta_e = -gamma_o + gamma_o* e11 + e_00
+
+            # e_00s.append(e_00)
+            # e11s.append(e11)
+            # delta_es.append(delta_e)
+
+        self.module.model.calibration = (E_Ds, E_Ss, E_ts)
 
     def export_calibration(self, filename: str) -> None:
         """This method is called when the export calibration button is pressed.

src/nqrduck_autotm/model.py

@@ -40,7 +40,12 @@ class S11Data:
     @property
     def gamma(self):
         """Complex reflection coefficient"""
-        return map(cmath.rect, (10 ** (-self.return_loss_db / 20), self.phase_rad))
+        if len(self.return_loss_db) != len(self.phase_rad):
+            raise ValueError("return_loss_db and phase_rad must be the same length")
+
+        return [cmath.rect(10 ** (-loss_db / 20), phase_rad) for loss_db, phase_rad in zip(self.return_loss_db, self.phase_rad)]
+
+
     
     def to_json(self):
         return {
@@ -72,6 +77,7 @@ class AutoTMModel(ModuleModel):
         super().__init__(module)
         self.data_points = []
         self.active_calibration = None
+        self.calibration = None
 
     @property
     def available_devices(self):

src/nqrduck_autotm/view.py

@@ -126,27 +126,48 @@ class AutoTMView(ModuleView):
         
         Args:
             data_points (list): List of data points to plot. 
+
+        @TODO: implement proper calibration. See the controller class for more information. 
         """
         frequency = data.frequency
         return_loss_db = data.return_loss_db
         phase = data.phase_deg
 
         gamma = data.gamma
-        # Calibration test:
-        #calibration = self.module.model.calibration
-        #e_00 = calibration[0]
-        #e11 = calibration[1]
-        #delta_e = calibration[2]
+        # Plot complex reflection coefficient
+        """ import matplotlib.pyplot as plt
+        fig, ax = plt.subplots()
+        ax.plot([g.real for g in gamma], [g.imag for g in gamma])
+        ax.set_aspect('equal')
+        ax.grid(True)
+        ax.set_title("Complex reflection coefficient")
+        ax.set_xlabel("Real")
+        ax.set_ylabel("Imaginary")
+        plt.show()
+         """
         
-        #y_corr = [(data_point - e_00[i]) / (data_point * e11[i] - delta_e[i]) for i, data_point in enumerate(y)]
-        #import numpy as np
-        #y = [data_point[1] for data_point in self.module.model.data_points]
-        #open_calibration = [data_point[1] for data_point in self.module.model.open_calibration]
-        #load_calibration = [data_point[1] for data_point in self.module.model.load_calibration]
-        #short_calibration = [data_point[1] for data_point in self.module.model.short_calibration]
+        magnitude_ax = self._ui_form.S11Plot.canvas.ax
+        # @ TODO: implement proper calibration
+        if self.module.model.calibration is not None:
+            # Calibration test:
+            import cmath
+            calibration = self.module.model.calibration
+            E_D = calibration[0]
+            E_S = calibration[1]
+            E_t = calibration[2]
 
-        #y_corr = np.array(y) - np.array(load_calibration)
-        #y_corr = y_corr - np.mean(y_corr)
+            # gamma_corr = [(data_point - e_00[i]) / (data_point * e11[i] - delta_e[i]) for i, data_point in enumerate(gamma)]
+            gamma_corr = [(data_point - E_D[i]) / (E_S[i] * (data_point - E_D[i]) + E_t[i]) for i, data_point in enumerate(gamma)]
+            """ fig, ax = plt.subplots()
+            ax.plot([g.real for g in gamma_corr], [g.imag for g in gamma_corr])
+            ax.set_aspect('equal')
+            ax.grid(True)
+            ax.set_title("Complex reflection coefficient")
+            ax.set_xlabel("Real")
+            ax.set_ylabel("Imaginary")
+            plt.show() """
+            return_loss_db_corr = [-20 * cmath.log10(abs(g + 1e-12))  for g in gamma_corr]
+            magnitude_ax.plot(frequency, return_loss_db_corr, color="red")
 
         phase_ax = self._ui_form.S11Plot.canvas.ax.twinx()
         phase_ax.set_ylabel("Phase (deg)")
@@ -154,7 +175,7 @@ class AutoTMView(ModuleView):
         phase_ax.set_ylim(-180, 180)
         phase_ax.invert_yaxis()
 
-        magnitude_ax = self._ui_form.S11Plot.canvas.ax
+        
         magnitude_ax.clear()
         magnitude_ax.set_xlabel("Frequency (MHz)")
         magnitude_ax.set_ylabel("S11 (dB)")