Microstrip‐line‐fed printed shorted ring‐slot antennas for circular polarization

Designs of circularly polarized printed shorted annual and square ring‐slot antennas are proposed. Circular polarization (CP) radiation of the shorted ring‐slot antennas is achieved by selecting a proper length of the shorted section in the ring slot, which is about 3.9 and 8% of the mean circumference of annular and square ring slots, respectively, and feeding the ring slot using a microstrip line 90° to the shorted section. Prototypes of the proposed designs have been implemented. Experimental results show that good CP radiation performances are observed, and the 3 dB axial‐ratio CP bandwidths obtained for the annular and square ring‐slot antennas can reach about 8.4 and 8.1%, respectively. Details of the proposed CP designs and obtained experimental results are presented and discussed. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 31: 137–140, 2001.