Compact 24 horn linear array

Thorn EMI Electronics has been involved in airborne radar for over fifty years, producing both demonstration systems and production radar such as the very successful Searchwater Maritime Reconnaissance Radar. The paper describes the design and performance of an antenna required for an airborne synthetic aperture radar demonstrator. The antenna uses a linear array of 24 horns to produce the azimuth pattern with a parabolic cylinder configured to form the pattern in the elevation plane. The waveguide feed to the 24 horns is arranged to produce both sum and difference patterns to allow for monopulse operation. There are restrictions imposed on the antenna, due to the airborne application, in terms of size and weight, hence the need to produce a compact overall structure. The antenna is required for high power operation, which requires pressurisation of the waveguide feed and feedhorns to prevent breakdown at high altitude