Axial-ratio bandwidth enhancement of asymmetric-CPW-fed circularly-polarised square slot antenna

Abstract

A novel broadband circularly-polarised (CP) square slot antenna fed by an asymmetric coplanar waveguide (CPW) from a corner of the slot is proposed. A CP bandwidth larger than 10% can be attained simply by using an inverted-L tuning stub protruded from the signal line of the CPW. With an additional pair of grounded strips implanted in the slot, the 3 dB axial-ratio bandwidth and the VSWR≤2 impedance bandwidth can be greatly raised to be as high as 30 and 35%, respectively.