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 circumfere nce of annular and square ring slots, respectively, and feeding the ring sl ot using a microstrip line 90 degrees 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 b andwidths 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 ob tained experimental results are presented and discussed. (C) 2001 John Wile y & Sons, Inc.