Focal axis resolver for offset reflector antennas

US4407001A · kind A · utility

Assignee

• The United States of America as represented by the Administrator of the National Aeronautics and Space Administration · US

Inventor

• Richard Schmidt · Kiel, DE

Key dates

• Filing date: Oct 2, 1981
• Grant date: Sep 27, 1983
• Expiry date: Oct 2, 2001

Classification

• Technology area (CPC H): Electricity
• CPC primary: H01Q19/132
• WIPO field: Telecommunications
• WIPO sector: Electrical engineering

Abstract

Method and apparatus for determining the focal axis (26) of an asymmetrical antenna (14) such as an offset paraboloid reflector whose physical rim (15) is not coincident with the boundary of the electrical aperture but whose focal point is known. A transmitting feed horn array (34) consisting of at least two feed horn elements (36, 38) is positioned asymmetrically on either side of an estimated focal axis (40) which is generally inclined with respect to the boresight axis (12) of the antenna. The feed horn array (34) is aligned with the estimated focal axis (40) so that the phase centers (CP.sub.1, CP.sub.2) of the two feed horn elements (36, 38) are located on a common line (42) running through the focal point (F) orthogonally with respect to the estimated focal axis. RF circuit means (44) are coupled to the feed horn elements for generating RF electric field components which are directed to the offset antenna (14) whereupon sum and difference radiation far field patterns (.SIGMA., .DELTA.) are generated and transmitted in a manner analogous to systems of the monopulse angle tracking type. The far field radiation patterns (.SIGMA., .DELTA.) are sensed by a far field detector (43) …