High-Frequency Circuit Model for the Incidence of Electromagnetic Waves on Hybrid Waveguide Structures

The purpose of this contribution is to show how an incident field impinging on a multiconductor transmission line (MTL) can be represented as a source term in a full-wave circuit model of that MTL. Results reported in literature (mainly for cables) are restricted to the quasi-TEM limit. Our approach allows one to determine up to which frequency the quasi-TEM limit is valid. As an example, we consider the case of a vertical electric dipole source above two coupled, perfectly conducting thick microstrips on top of a lossy substrate.