Fusing Leontovich Boundary Conditions and Scalar 2-D FEM to Compute Lid and Lateral Wall Losses in <i>H</i>-Plane Waveguide Devices

This letter introduces a 2-D finite-element method (FEM) for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">H</i>-plane waveguide devices, initially formulated for the ideal lossless case and then extended to include conductor losses. A scalar formulation naturally incorporates the Leontovich boundary condition on both the lid and lateral walls, with a first-order wavenumber correction at the lid walls and an additional matrix for lateral wall losses. Numerical results including an inductive filter and a K-band diplexer show excellent agreement with both analytic (when possible) and commercial software simulations based on 3D-FEM, confirming the method’s accuracy and efficiency for practical waveguide device analysis and design.