Bandwidth Enhancement of a Circularly Polarized Spiral Antenna using a Circular EBG Reflector

This paper describes the bandwidth enhancement of a circularly polarized (CP) spiral antenna using a circular electromagnetic band-gap (EBG) reflector for satellite communications and other wireless applications. The spiral antenna is placed at the front, and at the bottom is a circular EBG reflector with high-impedance surface properties. For comparison, circular EBG reflector was studied in comparison with circular PEC reflector. The antenna height from the bottom of the circular EBG reflector to the spiral antenna is small: 0.1 wavelengths at the lowest design frequency of 1.3 GHz. The circular EBG reflector contributes to a constant input impedance and small axial ratio (AR) throughout the design frequency range of 1.5–9.0 GHz (143%). The results of the analysis were verified by the measured results of the prototype antenna.