Microstrip-line-fed reactively loaded circularly polarized annular-ring slot antenna

Abstract

A simple and novel reactively loaded annular-ring slot antenna (ARSA) fed by a microstrip line is proposed and investigated for circularly polarized (CP) radiation. An appropriate reactive component, i.e. lumped capacitor/inductor, is introduced across the annular-ring slot at a proper position to achieve CP radiation. To validate the design concept, a capacitively loaded ARSA (CL-ARSA) and an inductively loaded ARSA (IL-ARSA) were implemented and measured, showing that good CP characteristics have been attained. The measured 3-dB axial ratio (AR) bandwidths for the CL-ARSA and IL-ARSA are 5.5 and 6.7%, respectively.