Bug fix in CoaxialLumpedPort.to_source

Author: weiliangjin2021

CHANGELOG.md

@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Fixed missing amplitude factor and handling of negative normal direction case when making adjoint sources from `DiffractionMonitor`.
 - Improved the robustness of batch jobs. The batch state, including all `task_ids`, is now saved to `batch.hdf5` immediately after upload. This fixes an issue where an interrupted batch (e.g., due to a kernel crash or network loss) would be unrecoverable.
 - Fixed warning for running symmetric adjoint simulations by port to not trigger when there is a single port.
+- Bug in `CoaxialLumpedPort` where source injection is off when the `normal_axis` is not `z`.
 
 ## [2.9.0] - 2025-08-04
 

tests/test_plugins/smatrix/test_terminal_component_modeler.py

@@ -386,6 +386,22 @@ def test_coaxial_port_snapping(tmp_path):
     check_lumped_port_components_snapped_correctly(modeler=modeler)
 
 
+@pytest.mark.parametrize("axis", [0, 1, 2])
+def test_coaxial_port_source_size(axis):
+    """Make sure source size is correct."""
+    port = CoaxialLumpedPort(
+        center=(0, 0, 0),
+        inner_diameter=1,
+        outer_diameter=2,
+        normal_axis=axis,
+        direction="+",
+        name="port",
+        impedance=50,
+    )
+    source = port.to_source(td.GaussianPulse(freq0=1e10, fwidth=1e9))
+    assert np.isclose(source.size[axis], 0)
+
+
 def test_power_delivered_helper(monkeypatch, tmp_path):
     """Test computations involving power waves are correct by manually setting voltage and current
     at ports using monkeypatch.

tidy3d/plugins/smatrix/ports/coaxial_lumped.py

@@ -192,7 +192,7 @@ def compute_coax_current(rin, rout, x, y):
 
         return CustomCurrentSource(
             center=center,
-            size=(self.outer_diameter, self.outer_diameter, 0),
+            size=size,
             source_time=source_time,
             name=self.name,
             interpolate=True,