A novel circularly polarised (CP), single-fed widebeam microstrip antenna is presented. The antenna consists of a corner-truncated square patch and a three dimensional circular ground structure. Simulated and measured results show that, owing to the ground structure, the 3 dB beamwidth of the CP radiation can reach more than 165o, which is about 85o, greater than that of a corresponding regular microstrip antenna. It is also shown that experimental results were in good agreement with the simulated performance. Details of the proposed 3-D circular ground structure are described, and the effects of various dimensions of the proposed ground structure on the beamwidth enhancement of CP radiation are studied.
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