A spiral antenna backed by an electromagnetic band-gap material

Abstract

A spiral antenna backed by an electromagnetic band-gap material, referred to as the EBG spiral antenna, has been analyzed using the finite-difference time domain method. The analysis shows that, even though the antenna height is less than one-quarter wavelength, the EBG spiral can radiate a CP wave. The spiral, which supports first mode radiation at 6 GHz, is found to have a frequency bandwidth of 11% for a 3-dB axial ratio criterion. Within this axial-ratio bandwidth, the gain variation is 4.1 dB.