A bent-ends spiral antenna above a fan-shaped electromagnetic band-gap structure

This paper describes radiation characteristics of a bent-ends two-arm Archimedean spiral antenna above a fan-shaped electromagnetic band-gap (EBG) structure. The EBG structure consists of fan-shaped EBG patch cells. The fan-shaped EBG patches are arranged homogeneously in the circumferential direction but are set non-homogeneously in the radial direction. The analysis is performed using the method of moment. It is revealed that wideband radiation characteristics, including input impedance and axial ratio, are mitigated by replacing a perfect electric conductor (PEC) reflector with the fan-shaped EBG structure.