SPHERICAL DOUBLE REFLECTOR ANTENNA

• US 3,852,765 A
• Filed: 12/19/1972
• Issued: 12/03/1974
• Est. Priority Date: 12/19/1972
• Status: Expired due to Term

• Current Assignee: Alcatel NV (Nokia Corporation)
• Original Assignee: Aaron D. Bresler, Emanuel Stein, Erdmann M. Otto
• Inventors: Bresler, Aaron D., Erdmann, M. Otto, Stein, Emanuel
• Primary Examiner(s): Gensler, Paul L.
• Application Number:
  US05/316,617
• Time in Patent Office: 714 Days
• Field of Search: 343/DIG.2,775,779,781,781A,781C,836,837,840
• US Class Current: 343/781.00R
• CPC Class Codes: H01Q 19/19 comprising one main concave reflecting surface associated with an auxiliary reflecting surface

Abstract

There is described a double reflector antenna arrangement having a fixed spherical-segment main reflector and at least one spherical subreflector surface concentrically arranged relative to the main reflector, which spherical/spherical double reflector antenna is particularly useful as a non-moving communication antenna capable of operating with one or more synchronous satellites. Multiple beam operation is effected by providing a feed with each spherical subreflector, wherein the position of the feeds relative to the main and subreflecting surfaces is optimized as a function of the antenna F/D ratio and especially the associated subreflector radius as defined by the spherical center point of the main reflector.

Claims

1. An antenna arrangement comprising a spherical main reflector surface, a spherical subreflector surface having a radius of curvature origin coincident with that for the main reflector, and at least one feed predeterminably arranged relative to said main and subreflector surfaces to illuminate said subreflector surface.

2. The antenna arrangement of claim 1 wherein in the case of a plurality of feeds being provided, each of said feeds is positioned relative to a particular portion of said subreflector surface.

3. The antenna arrangement of claim 1 wherein said spherical subreflector surface is provided by a plurality of spherical subreflectors each concentrically arranged relative to said main reflector surface and positioned a predetermined separation from a spherical center point defined by said spherical main reflector surface, and wherein a feed is provided for each of said plurality of spherical subrelfectors in effecting multiple-beam operation.

4. The antenna arrangement of claim 1 wherein said main reflector surface constitutes a spherical torus reflector and said subreflector surface constitutes a Cassegrain type spherical torus subreflector.

5. The antenna arrangement of claim 1 wherein in the case of providing a pair of feeds for dual-beam operation, the arrangement of said feeds relative to said main and subreflector surfaces is such as to provide a beam separation range of from approximately 2* to at least 50*.

6. The antenna arrangement of claim 5 wherein at least one of said plurality of feeds is adjustably positioned relative to said main and subreflector surfaces along a predetermined circular arc for providing the capability of continuous beam scanning in a predetermined plane without requiring movement of either of said main or subreflector surfaces.

7. In a multiple-beam double-reflector antenna arrangement, the combination comprising a spherical-segment main reflector, at least one sphericalsegment subreflector surface concentrically arranged relative to said main reflector, and a plurality of feeds predeterminably arranged relative to said main and subreflectors, each feed providing a beam for illuminating the subreflector surface.

8. The antenna arrangement of claim 7 wherein a plurality of spherical-segment subreflectors are provided in one-to-one correspondence with said plurality of feeds.

9. The antenna arrangement of claim 7 wherein said feeds constitute feed horns predeterminably positioned in terms of aperture relative to said main and subreflectors.

10. The antenna arrangement of claim 7 wherein for each feed provided in excess of one, a corresponding angular extension to both the main and subreflector surfaces is provided as defined by the angular separation between said feeds.

11. The antenna arrangement of claim 10 wherein for dual feeds being provided and arranged to provide a theta * beam separation, a corresponding angular addition of theta * to both the main and subreflectors is provided as related to the antenna spherical center point.

12. An energy radiating arrangement comprising a spherical main reflector surface defining a spherical center point 0, at least one spherical subreflector surface positioned a predetermined separation from said center point relative to said main reflector surface and arranged to be concentric therewith, at least one feed optimally positioned relative to said main reflector and subreflector, the entire geometry of the arrangement being concentric with respect to said spherical center point.

13. The antenna arrangement of claim 12 wherein said spherical center point 0 and said spherical main reflector define a main reflector radius R1 constituting the principal axis of the antenna arrangement, and wherein with a single spherical subreflector and feed being provided, said subreflector and feed are positioned to be centered on said main axis respectively at radii R2 and R3 as defined by 0<

R2<

R1 and R2<

R3<

R1, in which the location R3 of said feed is optimized in terms of antenna operating efficiency in dependence on the R1;

R2 radius relationship of said main and subreflectors.

14. The arrangement of claim 12 wherein said spherical center point 0 and said spherical main reflector define a radius R1 constituting the principal axis of the antenna arrangement, with said at least one spherical subreflector being centered thereon at a predetermined radius R2<

R1 relative to said center point 0 and wherein in the case of the antenna arrangement being provided with a plurality of feeds, said feeds are symmetrically arranged about said axis at a common radius R2<

R3<

R1 relative to said center point 0, in which R3 is selected to optimally position said feeds in terms of antenna phase error efficiency relative to the radius relationship R1;

R2 of said main and subreflectors.

15. The arrangement of claim 12 wherein said spherical center point 0 and said spherical main reflector define a radius R1 constituting the main axis of the antenna arrangement, and wherein in the case of the antenna arrangement being provdied with a plurality of spherical subreflecting surfaces and a corresponding plurality of feeds, said subreflectors and associated feeds are arranged about said main axis respectively at radii R2 and R3 as defined by 0<

R2<

R1 and R2 <

R3<

R1, in which R3 is selected to optimally position said feeds in terms of antenna phase error efficiency relative to the radius relationship R1;

R2 of said main and subreflectors.

16. In an antenna system, the combination of a spherical maIn reflector surface which defines a spherical center point and a radius R1, and a spherical subreflector surface, the radius of curvature origin thereof being coincident with that of the main reflector and which is predeterminably positioned at a radius R2<

R1 relative to said center point, and further comprising at least one feed positioned, in terms of antenna efficiency, to be optimally arranged for illuminating said subreflector at a predetermined separation from the vertex of said subreflector as a function of the radii R1 and R2.

17. A double-reflector antenna arrangement comprising a fixed spherical main reflector of predetermined physical dimensions composed of a multiplicity of reflecting panels having substantially identical spherical reflecting surface curvature arranged in mosaic form to effect a substantially continuous spherical main reflecting surface, at least one spherical subreflector mounted to be concentrically arranged relative to said main reflector at a predetermined separation therefrom, and a separate feed for each subreflector predeterminably mounted relative thereto to form a feed/subreflector assembly arrangement requiring only feed positioning to implement beam steering and tracking;

said feed/subreflector assembly constitutes a Cassegrain type feed/spherical subreflector assembly, and wherein the main and subreflectors are concentric spherical surfaces relative to a common spherical center so as to provide beam pointing as a function of the position of the feed on a spherical radius relative to the main spherical surface; and

the total surface area required for said spherical main reflector for multiple beam operation is determined as a function of antenna aperture and maximum beam separation only and independent of the number of beams.

18. A method of optimizing a spherical/spherical double-reflector radiating arrangement, comprising the steps of determining, in relation to a spherical main reflector, the position of a concentrically arranged spherical subreflector in terms of the spherical center point defined by the main reflector and placing the subreflector thereat, wherein the upper limit of the position of the spherical subreflector relative to the spherical main reflector center point is determined by the maximum allowable blocking loss which in turn is further defined by the subreflector-to-main reflector diameter ratio, and wherein the lower limit is determined by the requirement that blocking due to the feed of the antenna not exceed that of the subreflector;

and determining the feed location relative to the vertex of the spherical subreflector for a given F/D ratio so as to provide substantially zero path-length error proximate the aperture edge of the spherical main reflector, wherein the optimum feed to subreflector separation is primarily a function of the position of the subreflector relative to the main reflector spherical center point, with second order dependence on the F/D ratio.