LAUSR

In this Letter, a fork-shaped wideband circularly polarised antenna is proposed. Using the fork-shaped metal wall structure and 45° deflection, the wideband circular polarisation performance of the proposed antenna is achieved. Besides, an antenna prototype working at W-band is processed. The right-hand circularly polarised bandwidth (axial ratio < 3 dB) and impedance bandwidth (S11 < −10 dB) of the antenna are both measured as 38.1% (75–110 GHz). The measured gain is 10.7–14.2 dBic (±0.5 dBic). The proposed antenna exhibits a simple structure, which is easy to process. This proposed wideband circularly polarised horn antenna can have wide applications for millimetre and sub-millimetre wave bands.