EBG Structure With Wide Defect Band for Broadband Cavity Antenna Applications

In this letter, a new electromagnetic band gap (EBG) structure is proposed. It is constructed by double-layer frequency selective surfaces (FSS) periodically arranged in the z-direction. A periodicity defect is introduced in the middle of the structure. Resulted EBG structure with defect is composed of two double-layer FSS with wavelength spacing between them. Due to the presence of the defect, an allowed frequency band is created within the EBG structure band gap. The width of the formed defect band is increased compared to that of classical EBG structures with defect. The new material composed of a double-layer FSS is applied in the design of a resonator antenna. The resonator, formed between the double-layer FSS and a metallic ground, is fed by a patch source placed at the proximity of the ground. The antenna bandwidth is significantly improved by virtue of employing the new structure of wider allowed band. The participation of each FSS layer in the antenna bandwidth enhancement is described. An antenna application at 5 GHz is shown.