modified voltage computation to avoid interpolation at conductor inte…

…rface

tidy3d/plugins/smatrix/component_modelers/terminal.py

@@ -1,4 +1,5 @@
 """Tool for generating an S matrix automatically from a Tidy3d simulation and lumped port definitions."""
+
 from __future__ import annotations
 
 from typing import Tuple, Dict
@@ -193,16 +194,25 @@ def port_voltage(port: LumpedPort, sim_data: SimulationData) -> xr.DataArray:
             e_component = "xyz"[port.voltage_axis]
             field_data = sim_data[f"{port.name}_E{e_component}"]
             e_field = field_data.field_components[f"E{e_component}"]
+
+            # Remove E field outside the port region
+            e_field = e_field.sel(
+                {
+                    e_component: slice(
+                        port.bounds[0][port.voltage_axis], port.bounds[1][port.voltage_axis]
+                    )
+                }
+            )
             e_coords = [e_field.x, e_field.y, e_field.z]
-            # interpolate E locations to coincide with port bounds along the integration path
-            e_coords_interp = {
-                e_component: np.linspace(
-                    port.bounds[0][port.voltage_axis],
-                    port.bounds[1][port.voltage_axis],
-                    len(e_coords[port.voltage_axis]),
-                )
-            }
-            e_field = e_field.interp(**e_coords_interp)
+            # Integration is along the original coordinates plus two additional endpoints corresponding to the precise bounds of the port
+            e_coords_interp = np.array([port.bounds[0][port.voltage_axis]])
+            e_coords_interp = np.concatenate((e_coords_interp, e_coords[port.voltage_axis].values))
+            e_coords_interp = np.concatenate((e_coords_interp, [port.bounds[1][port.voltage_axis]]))
+            e_coords_interp = {e_component: e_coords_interp}
+            # Use extrapolation for the 2 additional endpoints
+            e_field = e_field.interp(
+                **e_coords_interp, method="linear", kwargs={"fill_value": "extrapolate"}
+            )
             voltage = -e_field.integrate(coord=e_component).squeeze(drop=True)
             # Return data array of voltage with coordinates of frequency
             return voltage
@@ -271,13 +281,17 @@ def port_current(port: LumpedPort, sim_data: SimulationData) -> xr.DataArray:
             h_max_bound = hcap_plus.coords[h_component].values
             h_coords_interp = {
                 h_component: np.linspace(
+                    # port.bounds[0][port.current_axis],
+                    # port.bounds[1][port.current_axis],
                     h_min_bound,
                     h_max_bound,
                     len(h_coords[port.current_axis] + 2),
                 )
             }
             # Integration that corresponds to the tangent H field
             h_field = h_field.interp(**h_coords_interp)
+            # h_field = h_field.sel({h_component: slice(port.bounds[0][port.current_axis], port.bounds[1][port.current_axis])})
+            # h_field = h_field.interp(**h_coords_interp, kwargs={"fill_value": "extrapolate"})
             current = h_field.integrate(coord=h_component).squeeze(drop=True)
 
             # Integration that corresponds with the contribution to current from cap contours