Leaky wave phenomena of a conductor‐back dielectric slab covered with a two‐dimensionally electromagnetic band gap superstrate

Abstract

This paper presents the leaky wave phenomena associated with a waveguide structure that consists of a conductor‐back dielectric slab covered with a superstrate made up of a two‐dimensionally (2‐D) electromagnetic band gap (EBG) structure. A guided wave has its energy bounced back and forth between the metallic ground plane and the EBG structure that is taken as a frequency‐selective reflection mirror. Because of the finite thickness of the 2‐D EBG superstrate, the guided wave will leak or radiate some of its energy into the air region above the waveguide structure to become a leaky wave. By the mode‐matching method and the transverse resonance technique, the overall waveguide structure is formulated as a rigorous electromagnetic boundary value problem to yield an exact dispersion relation of the waveguide so that the complex propagation constant of a guided mode can be accurately determined, including the phase and attenuation constants. Additionally, the electric field distribution inside the waveguide and the far‐field radiation pattern were also calculated to demonstrate the leaky wave phenomena of this waveguide from a microscopic point of view. On the basis of the excitation of leaky waves, the phenomenology concerning a class of directive antennas with EBG structure as superstrate was clarified in this research.