Perfect conversion of a TM surface-wave into a TM leaky-wave by an isotropic periodic metasurface printed on a grounded dielectric slab

TL;DR

This paper provides an exact, lossless metasurface design that perfectly converts TM surface waves into leaky waves without higher-order mode excitation, enabling efficient wave radiation.

Contribution

It introduces a novel, practical metasurface solution that achieves perfect TM surface-to-leaky wave conversion considering grounded slab effects, unlike previous impenetrable boundary approaches.

Findings

Achieves perfect TM surface wave to leaky wave conversion

Ensures no higher-order evanescent modes near the surface

Design varies from inductive to capacitive reactance at resonance

Abstract

This paper presents an exact solution for a perfect conversion of a TM-polarized surface wave (SW) into a TM-polarized leaky-wave (LW) using a reciprocal and lossless penetrable metasurface (MTS) characterized by a scalar sheet impedance, located on a grounded slab. In contrast to known realizations of leaky-wave antennas, the optimal surface reactance modulation which is found here ensures the absence of evanescent higher-order modes of the field Floquet-wave expansion near the radiating surface. Thus, all the energy carried by the surface wave is used for launching the single inhomogeneous plane wave into space without accumulation of reactive energy in the higher-order modes. It is shown that the resulting penetrable MTS exhibits variation from an inductive to a capacitive reactance passing through a resonance. The present formulation complements a previous paper of the authors in which a perfect conversion from TM-polarized SW to TE-polarized LW was found for impenetrable boundary conditions. Here, the solution takes into account the grounded slab dispersion and it is convenient for practical implementation.