Scanable antenna arrangements capable of producing a large image of a small array with minimal aberrations
First Claim
1. A multiple reflector antenna arrangement comprisinga main parabolic reflector (10) comprising a predetermined exit aperture (DO) and a geometric focal point (F);
- a parabolic subreflector (12) comprising a geometric focal point (F or F1) and disposed confocally with a next previous reflector along a transmission path of the atenna arrangement in the direction toward the main parabolic reflector from said parabolic subreflector; and
a feed array (14) comprising a plurality of feed elements and directed at the parabolic subreflectorcharacterized in thatthe feed elements of the feed array are disposed substantially on a plane (ξ
1) which is a conjugate plane relative to the exit aperture of the main reflector such that a ray incident at a central point (Co) of the main reflector from any direction, when reflected by said main reflector essentially intersects the conjugate plane at said feed array at a central point (C1).
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Abstract
The present invention relates to antennas which have reflector arrangements that produce a large image with minimal aberrations at the exit aperture thereof of a small feed array. In the present arrangement, the feed array is placed at the conjugate plane relative to the exit aperture of a geometrically confocal reflector system comprising a parabolic main reflector and a parabolic subreflector so that exact imaging of the array is obtained at the exit aperture. In such arrangements, alignment and surface accuracy errors of the various reflectors can be easily corrected by appropriately changing the phase or the position of the associated elements of the feed array. A three-reflector arrangement having sequential geometric confocality is disclosed which also alters the focal length of the main reflector sufficiently to permit the inclusion of polarization and/or frequency diplexing means in the overall reflector system.
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Citations
8 Claims
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1. A multiple reflector antenna arrangement comprising
a main parabolic reflector (10) comprising a predetermined exit aperture (DO) and a geometric focal point (F); -
a parabolic subreflector (12) comprising a geometric focal point (F or F1) and disposed confocally with a next previous reflector along a transmission path of the atenna arrangement in the direction toward the main parabolic reflector from said parabolic subreflector; and a feed array (14) comprising a plurality of feed elements and directed at the parabolic subreflector characterized in that the feed elements of the feed array are disposed substantially on a plane (ξ
1) which is a conjugate plane relative to the exit aperture of the main reflector such that a ray incident at a central point (Co) of the main reflector from any direction, when reflected by said main reflector essentially intersects the conjugate plane at said feed array at a central point (C1). - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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5. A multiple reflector antenna arrangement according to claim 4
characterized in that the second focusing subreflector comprises a hyperboloid reflecting surface. -
6. A multiple reflector antenna arrangement according to claim 4
characterized in that the main reflector, parabolic subreflector and second focusing subreflector are arranged in an offset configuration. -
7. A multiple reflector antenna arrangement according to claims 1, 2, or 4
characterized in that predetermined feed elements of the feed array are disposed slightly away from the conjugate plane in a manner to provide a phase distribution contour along the conjugate plane which negates phase differences introduced in a reflected planar wavefront by imperfections in the reflecting surface of the main reflector. -
8. A multiple reflector antenna arrangement according to claims 1, 2, or 4 wherein each feed element of the feed array is connected to a separate feed line capable of bidirectionally propagating signals between the associated feed element and a circuit means
characterized in that time delay means are mounted in predetermined ones of the feed lines connected to the plurality of feed elements capable of providing a time delay in signals propagating thereon sufficient to compensate for phase differences which are introduced in a reflected planar wavefront by imperfections in the reflecting surface of the main reflector.
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Specification
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- Resources
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Current AssigneeBell Telephone Laboratories, Inc. (Nokia Corporation)
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Original AssigneeBell Telephone Laboratories, Inc. (Nokia Corporation)
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InventorsDragone, Corrado, Gans, Michael J.
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Primary Examiner(s)Moore, David K.
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Application NumberUS05/906,737Time in Patent Office727 DaysField of Search343/781 CA, 343/781 R, 343/781 P, 343/779, 343/837, 343/839, 343/840US Class Current343/781.00PCPC Class CodesH01Q 19/17 the primary radiating sourc...H01Q 19/192 with dual offset reflectors
