Multimode corrugated waveguide feed for monopulse radar

The paper describes the behaviour of a multimode corrugated feed for use in monopulse radar. Four square input waveguides are used to excite sum-and difference-channel modes. With appropriate choice of parameters it is possible to generate radiation patterns with low crosspolarisation thus allowing the polarisation characteristics of a target to be obtained. The results of an anlysis of the relevant waveguide discontinuity problem are presented and a means to compensate phase differences between modes is also described. Some preliminary experimantal results are found to be in accord with theory.