US 4,626,863 AGranted

Low side lobe Gregorian antenna

AssigneeAndrew Corporation

InventorsCharles M. Knop, Edward L. Ostertag, Yuk-Bun Cheng

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Abstract

A microwave antenna comprising the combination of a paraboloidal main reflector; a subreflector located such that the paraboloidal main reflector and the subreflector have a common focal point lying between the main reflector and the subreflector; a feed horn for transmitting microwave radiation (preferably symmetrically) to, and receiving microwave radiation from, said subreflector; and a shield connected to the peripheral portion of the subreflector and having an absorbing surface which reduces side lobe levels both by capturing the feed horn spillover energy and by reducing the diffraction of microwave radiation from the edge of the subreflector. The shield is preferably formed as a continuous axial projection extending from the periphery of the subreflector toward the main reflector substantially parallel to the axis of the feed horn. The reflective surface of the subreflector is suitably a section of an approximate ellipse.

Claims5

Dependent claims

A microwave antenna comprising the combination of:

a paraboloidal main reflector having an axis and a focal point F;
a subreflector forming a surface of revolution about the axis of said main reflector and having a focal point between said main reflector and said subreflector and substantially coincident with the focal point of said main reflector;
a feed horn extending along the axis of said main reflector for transmitting microwave radiation to, and receiving microwave radiation from, said subreflector along a feed horn beam;
and
a first shield extending from the periphery of said subreflector toward said main reflector, parallel to the axis of the main reflector, for reducing side lobe levels, said first shield terminating outside of the beam passing between the subreflector and the main reflector, a second shield extending from the periphery of said main reflector and parallel to the axis of the main reflector, said first shield intercepting that portion of the feed horn beam which is not intercepted by either said subreflector or said second shield.

2 more elements

Dependencies are inferred from the claim text.