From 1b80432f91073aefea00a708b36fdc8db372d1a3 Mon Sep 17 00:00:00 2001
From: dmarek <damian@flexcompute.com>
Date: Thu, 23 May 2024 14:28:10 -0400
Subject: [PATCH] improved test coverage of microstrip plugin and removed
 deprecated typing

---
 tests/test_plugins/test_microwave.py          | 66 ++++++++++++++++++-
 .../microwave/models/coupled_microstrip.py    |  5 +-
 tidy3d/plugins/microwave/models/microstrip.py |  3 +-
 3 files changed, 67 insertions(+), 7 deletions(-)

diff --git a/tests/test_plugins/test_microwave.py b/tests/test_plugins/test_microwave.py
index bad8ff8941..2d8e8e1a66 100644
--- a/tests/test_plugins/test_microwave.py
+++ b/tests/test_plugins/test_microwave.py
@@ -1,5 +1,11 @@
+"""Test the microwave plugin."""
+
 import pytest
 import numpy as np
+import pydantic.v1 as pydantic
+
+from skrf import Frequency
+from skrf.media import MLine
 
 import tidy3d as td
 from tidy3d import FieldData
@@ -9,11 +15,12 @@
     CurrentIntegralAxisAligned,
     ImpedanceCalculator,
 )
-import pydantic.v1 as pydantic
+
+from tidy3d.plugins.microwave.models import microstrip, coupled_microstrip
+
 from tidy3d.exceptions import DataError
 from ..utils import run_emulated
 
-
 # Using similar code as "test_data/test_data_arrays.py"
 MON_SIZE = (2, 1, 0)
 FIELDS = ("Ex", "Ey", "Hx", "Hy")
@@ -303,3 +310,58 @@ def impedance_of_stripline(width, height):
     assert np.all(np.isclose(Z1, analytic_impedance, rtol=0.02))
     assert np.all(np.isclose(Z2, analytic_impedance, atol=3.5))
     assert np.all(np.isclose(Z3, analytic_impedance, atol=3.5))
+
+
+def test_microstrip_models():
+    width = 3.0
+    height = 1.0
+    thickness = 0.0
+    eps_r = 4.4
+
+    # Check zero thickness parameters
+    Z0, eps_eff = microstrip.compute_line_params(eps_r, width, height, thickness)
+    freqs = Frequency(start=1, stop=1, npoints=1, unit="ghz")
+    mline = MLine(frequency=freqs, w=width, h=height, t=thickness, ep_r=eps_r, disp="none")
+
+    assert np.isclose(Z0, mline.Z0[0])
+    assert np.isclose(eps_eff, mline.ep_reff[0])
+
+    # Check end effect length computation
+    dL = microstrip.compute_end_effect_length(eps_r, eps_eff, width, height)
+    assert np.isclose(dL, 0.54, rtol=0.01)
+
+    # Check finite thickness parameters
+    thickness = 0.1
+    Z0, eps_eff = microstrip.compute_line_params(eps_r, width, height, thickness)
+    mline = MLine(frequency=freqs, w=width, h=height, t=thickness, ep_r=eps_r, disp="none")
+
+    assert np.isclose(Z0, mline.Z0[0])
+    assert np.isclose(eps_eff, mline.ep_reff[0])
+
+
+def test_coupled_microstrip_model():
+    w1 = 1.416
+    w2 = 2.396
+    height = 1.56
+    g1 = 0.134
+    g2 = 0.386
+    eps_r = 4.3
+    # Compare to:   Taoufik, Ragani, N. Amar Touhami, and M. Agoutane. "Designing a Microstrip coupled line bandpass filter."
+    #               International Journal of Engineering & Technology 2, no. 4 (2013): 266.
+    # and notebook "CoupledLineBandpassFilter"
+
+    (Z_even, Z_odd, eps_even, eps_odd) = coupled_microstrip.compute_line_params(
+        eps_r, w1, height, g1
+    )
+    assert np.isclose(Z_even, 101.5, rtol=0.01)
+    assert np.isclose(Z_odd, 38.5, rtol=0.01)
+    assert np.isclose(eps_even, 3.26, rtol=0.01)
+    assert np.isclose(eps_odd, 2.71, rtol=0.01)
+
+    (Z_even, Z_odd, eps_even, eps_odd) = coupled_microstrip.compute_line_params(
+        eps_r, w2, height, g2
+    )
+    assert np.isclose(Z_even, 71, rtol=0.01)
+    assert np.isclose(Z_odd, 39, rtol=0.01)
+    assert np.isclose(eps_even, 3.42, rtol=0.01)
+    assert np.isclose(eps_odd, 2.80, rtol=0.01)
diff --git a/tidy3d/plugins/microwave/models/coupled_microstrip.py b/tidy3d/plugins/microwave/models/coupled_microstrip.py
index 8ce0e3a814..76467c911b 100644
--- a/tidy3d/plugins/microwave/models/coupled_microstrip.py
+++ b/tidy3d/plugins/microwave/models/coupled_microstrip.py
@@ -9,7 +9,6 @@
 
 import numpy as np
 from . import microstrip
-from typing import Tuple
 
 
 def _epsilon_e_even(relative_permittivity: float, width: float, height: float, gap: float) -> float:
@@ -51,7 +50,7 @@ def _z0_even_odd(
     e_eff_odd: float,
     z0: float,
     e_eff: float,
-) -> Tuple[float, float]:
+) -> tuple[float, float]:
     """Computes the characteristic impedance of the even and odd modes for coupled microstrip lines.
     Equations 8 and 9 [1]"""
     normalized_width = width / height
@@ -79,7 +78,7 @@ def _z0_even_odd(
 
 def compute_line_params(
     relative_permittivity: float, width: float, height: float, gap: float
-) -> Tuple[float, float, float, float]:
+) -> tuple[float, float, float, float]:
     """Computes an approximation for the parameters of coupled microstrip lines
     assuming the quasistatic regime and 0 thickness [1].
 
diff --git a/tidy3d/plugins/microwave/models/microstrip.py b/tidy3d/plugins/microwave/models/microstrip.py
index 7f0ed096a6..aad29fd7d6 100644
--- a/tidy3d/plugins/microwave/models/microstrip.py
+++ b/tidy3d/plugins/microwave/models/microstrip.py
@@ -14,7 +14,6 @@
 import numpy as np
 
 from ....constants import ETA_0
-from typing import Tuple
 
 
 def _f(normalized_width: float) -> float:
@@ -73,7 +72,7 @@ def _wcorr_mixed(width_correction_homo: float, relative_permittivity: float) ->
 
 def compute_line_params(
     relative_permittivity: float, width: float, height: float, thickness: float
-) -> Tuple[float, float]:
+) -> tuple[float, float]:
     """Computes an approximation for the characteristic impedance and effective
     electric permittivity of a microstrip line [1].