Quasi-equispaced slot arrays with extremely low crosspolarisation

Crosspolarisation well below the prescribed side-lobe level of a travelling-wave array may be achieved, without using additional discriminating structures, by applying a circular, dielectric-filled waveguide with a sequence of circumferential gaps. Operated in the TM01 mode, a computer-designed X band prototype having a directivity of 27 dB was found to secure crosspolarisation of less than ¿34 dB.