Provision of X-band illumination in a Ku-band tracking antenna

The 9LV Mk3 Director-Tracking Radar, operating in the Ku-band was designed as a high accuracy, general purpose tracker for all sizes of warships. The requirements encompassed not only gun fire control but also control of surface-to-air missiles (SAMD). Shipboard, medium range SAMs designed for semi-active guidance require the target to be illuminated by X-band CW energy, normally using a high gain, narrow beamwidth antenna. It is of course highly desirable to use the 1 m diameter aperture of the Ku-band antenna also for the X-band. A condition for so doing is that the high performance at Ku-band, e.g. boresight stability and very low sidelobes, is not degraded. Requirements at the X-band are, on the other hand, considerably more moderate. The paper describes an ongoing effort, where some fundamental problems have been solved but all details not yet completed