Polarisation-agile, evanescent open-ended waveguide antenna

A polarisation-agile, evanescent waveguide-based antenna element is proposed, which allows below and above waveguide cutoff operation from 1.54-1.89 GHz for return loss <;-10dB i.e. a bandwidth of 20.4%. Square evanescent waveguide with 1.7 GHz cutoff is shunt loaded with flat metal strips, positioned across the aperture of the waveguide. It is shown that linear or circular polarisation may be achieved depending on the excitations supplied to the input ports of the antenna.