The Marvels of Electromagnetic Band Gap (EBG) Structures

Abstract

Artists and scientists alike have been fascinated by the existence of periodic structures in nature. When these structures interact with electromagnetic waves many unique features result. Observables are characteristics such as frequency stop-bands, pass-bands, and band-gaps. Various terminology have been used to classify these structures depending on the domain of the applications in filter designs, gratings, frequency selective surfaces (FSS), photonic crystals and band-gaps (PBG), etc. We prefer to classify them under the broad terminology of “Electromagnetic Band-gaps (EBG)”. Recently, many researchers have adopted this terminology. Broadly speaking, EBG structures are 3-D periodic objects that prevent the propagation of the electromagnetic waves in a specified band of frequency for all angles of arrival and for all polarization states of electromagnetic waves. In practice, however, it is very difficult to obtain such complete band-gap structures and partial band-gaps are achieved. Filters typically cover the scalar situation and single angle of arrival. FSS typically cover limited angles of arrival and respond differently to polarization states. PBG typically cover in-plane angles of arrival and also sensitive to polarization states. Surveying the literature, one finds that FSS terminology has been widely used in the microwave community while PBG terminology has been widely applied in the optical community. This overview paper presents a powerful computational engine utilizing Finite Difference Time Domain (FDTD) technique integrated with novel extrapolating algorithms to illustrate the marvels of EBG structures. The paper addresses structures such as (a) FSS structures, (b) PBG crystals, (c) smart surfaces for communication antenna applications, (d) surfaces with perfectly magnetic conducting properties (PMC), (e) creation of materials with negative permittivity and negative permeability, (f) surfaces with reduced edge diffraction effects and (g) reduction of mutual coupling among array antenna elements. Some representative applications of these structures are highlighted. In the last several years, there have been numerous published conference papers and journal articles dealing with the characterizations and applications of EBG structures. This paper is based on some of the results published by the author and his co-workers in the cited references. The reader is encouraged to perform detailed literature search to learn more about this area.