Ioannis Koufogiannis

On the Development and Evaluation of Spatial-Domain Green’s Functions for Multilayered Structures With Conductive Sheets

This work focuses on Greens functions (GFs) of planar multilayered structures that may include an arbitrary number of conductive sheets. The spectral-domain GFs are derived through an automatized strategy based on the propagator matrix technique, while the spatial-domain counterparts are evaluated using a novel, efficient, and error controlled numerical method. All of the procedures remain general in order to accommodate for the tensorial nature of the surface conductivity of the sheets. Numerical examples of GFs for the mixed potential integral equation method are provided, validating the proposed algorithms.

Microwave gas breakdown in elliptical waveguides

This paper analyzes the microwave gas discharge within elliptical waveguides excited by the fundamental mode. The Rayleigh-Ritz method has been applied to solve the continuity equation. The eigenvalue problem defined by the breakdown condition has been solved and the effective diffusion length of the elliptical waveguide has been calculated, what is used to find the corona threshold. This paper extends the microwave breakdown model developed for circular waveguides and shows the better corona withstanding capabilities of elliptical waveguides. The corona breakdown electric field threshold obtained with the variational method has been compared with the one calculated with the Finite Elements Method, showing excellent agreement.