A versatile, multibeam antenna for airborne radar applications

This paper describes an X-band antenna for use in an experimental airborne radar system. The antenna is designed to radiate either linear or circular (CP) polarisation and generates monopulse sum (Σ) and difference (Δ) beams in azimuth. The antenna has two interchangeable gain modes of operation. Achieving the exacting antenna performance required a close interaction between electrical and mechanical design. Low cross-polar and sidelobe levels have been achieved through precision manufacturing of the antenna components. High performance is achieved from within a compact (470 mm high) radome by using CAD techniques to ensure efficient use of the swept volume. The mass and moments of inertia have been minimised, in order to be compatible with a 360° rotating scanner platform, by extensive use of CAD and stress-analysis tools