A W-band Broadband Cassegrain Antenna with Polarisation and OAM Multiplexing

A broadband dual-polarisation and three-mode OAM cassegrain antenna in W-band is proposed. The antenna consists of two parts. One is a dual-polarised open-ended square waveguide antenna double-ring antenna array as a feed, which is designed to generate OAM beams with modes of l= ±1 and +2, and the other is a cassegrain reflector, which is designed to converge the OAM beams. The proposed antenna has a 10dB impendance bandwidth beyond 24.9%, gains better than 26.6dBi, side-lobe levels lower than −10.7dB, and cross-polarisation levels lower than −15dB.