Resonance characteristics and field enhancement in cylindrical electromagnetic bandgap structures

摘要

Recently novel electromagnetic bandgap (EBG) structures — cylindrical EBG structures — have received a growing attention because of their potential applications to the designs of beam forming and multibeam antennas [1]. In this paper, excitation of the cylindrical EBG structure by line source located at the origin of the structure and by TM polarized plane waves is studied. Transmission spectra of eccentric cylindrical EBG structures are investigated using a rigorous and accurate semi-analytical method based on the cylindrical Floquet mode expansion. The method takes into account all of the cylindrical Floquet modes and their interactions between the layers [2–4]. The resonance and stopbands of the transmission into the several principle Floquet modes are studied. We have numerically shown that when cylindrical EBG structure of eccentric configuration is illuminated by a plane wave of particular resonance frequency, enhancement or “shadowing” effects of the field inside the EBG structure are observed and these effects strongly depend on the angle of incidence of the plane waves. Enhancement and “shadowing” effects of the field could be explained from the Reciprocity Relation for the cylindrical structures. To the best of authors' knowledge, such studies are performed first time.