Square slot antenna with two spiral slots loaded for broadband circular polarisation

摘要

A simple design of a broadband circularly polarised (CP) square slot antenna with two loaded spiral slots is proposed. The CP operation is realised by embedding a pair of inverted-L-shaped strips around two opposite corners of the square slot and can be markedly improved by loading two spiral slots in the ground plane. By using these modifications, the 3 dB axial ratio bandwidth (ARBW) of about 5 GHz, which is chiefly ascribed to the existence of two spiral slots and impedance bandwidth of larger than 111% are achieved. However, the overall size of the antenna is only 20 × 20 × 0.8 mm, it covers wider ARBW than many of the designed slot antennas.