Abstract: A broadband (8-18 GHz) radomed horn antenna system comprises a conical horn having broadband slots on the inner surface and a radome having a frusto-conical side wall and a spherically shaped transverse wall inserted into the horn. The radome wall is thin relative to operating wavelength. The radome side wall fits snugly against the inner surface of the horn wall so that transverse wall is proximate to the horn feed port with its convex side facing toward the horn aperture. The cylindrical feed guide contains a higher order hybrid mode suppressor which maintains a substantially uniform radiation pattern over the operating band with an acceptable insertion loss.

Abstract: Broadband (8-18 GHz) operation of a horn antenna with broadband corrugations is achieved by provision of dissipative TM.sub.11 mode suppressor means in the input waveguide feed to the horn. For a conical horn the input feed waveguide is circular and the mode suppressor means comprises a pair of axially extending diametrically spaced conductive wires or rods supported within the waveguide in dielectric foam, or alternatively, a cylindrical resistance card similarly supported coaxially with the waveguide. For a square corrugated horn of this type, the input waveguide is square and the mode suppressor means comprises a pair of parallel spaced axially extending resistance cards located in the planes of the magnetic field nulls in the waveguide.