Insular-image guide-fed short backfire antenna

A short backfire antenna using an insular-image waveguide feed that is compatible with the microwave dielectric integrated-circuit technology is presented. The antenna is made feasible by providing an annular gap between the insular image guide and the metal reflector at the feed point. The important parameters of the antenna are experimentally optimised to give a maximum gain of 12.5 dB at the design frequency of 10 GHz. The measured radiation patterns are compared with the theoretical patterns computed from the near-field amplitude distribution. This type of antenna can find extensive applications at millimetre-wave frequencies.