| 摘要 |
<p>A horn antenna suitable for an amplitude-comparison broadband direction-finding system with 360° azimuth coverage has a horn with a wide angle of flare in a plane normal to the z-axis of a cylindrical co-ordinate system and an aperture (5) which is concave, suitably cylindrical, as seen from that axis. In order to provide a substantially constant beamwidth over a broad frequency range, which may be as wide as 7 : 1, the horn comprises means (7) for launching into the horn towards its aperture (5) a substantially pure lowest order radial mode having its electric field in a direction parallel to the z-axis, the means acting substantially as a line source coincident with the z-axis. The flare angle may be 180 degrees, and the launching means (7) may comprise an electric probe extending substantially along the z-axis.</p> |
