Propagation and radiation behaviour of a longitudinally slotted horn with dielectric-filled slots

It is proposed that the slots of a longitudinally slotted horn be filled with a dielectric material. This is shown to considerably reduce the required slot depths for achieving low crosspolarisation; thus more feasible and economic design of such a horn is possible. Design curves for the modal propagation constants of the first two modes against the frequency, the dielectric constant of the slot filling material and the geometrical constants of the horn are presented. The co- and cross-polar radiation patterns are calculated, and it is found that peak crosspolar level < ¿¿ 50 dB can be achieved at certain frequencies and a level < ¿¿ 30 dB can be achieved over about 13% bandwidth.