Antenna having hemispherical radiation optimized for peak gain at horizon

• US 6,219,004 B1
• Filed: 06/11/1999
• Issued: 04/17/2001
• Est. Priority Date: 06/11/1999
• Status: Expired due to Fees

• Current Assignee: Hanger Solutions, LLC (IP Investments Group LLC)
• Original Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Inventors: Johnson, Jeffrey A.
• Primary Examiner(s): Wimer, Michael C.
• Application Number:
  US09/329,852
• Time in Patent Office: 676 Days
• Field of Search: H01/Q 1.912, 343/705, 343/781.R, 343/834, 343/781.P
• US Class Current: 343/781.00P
• CPC Class Codes: H01Q 1/28 Adaptation for use in or on aircraft, missiles, satellites, or balloons
• CPC Class Codes: H01Q 19/134 Rear-feeds; Splash plate feeds
• CPC Class Codes: H01Q 19/19 comprising one main concave reflecting surface associated with an auxiliary reflecting surface

Abstract

An antenna, such as may be employed for air-to-ground link hemispherical communication coverage, comprises a shaped ring focus type subreflector, that is rotationally symmetric about the boresight axis of a feed horn to which communication equipment on board an unmanned aerial vehicle is coupled. There is no main reflector associated with the shaped subreflector, so that rays from the subreflector, which emanate in a generally hemispherical pattern, are not intercepted. The generally hemispherical radiation pattern extends toward the horizon and encompasses a ground station. The subreflector is preferably shaped such that the hemispherical radiation pattern has a peak gain profile that extends from a first prescribed elevation differential slightly above the horizon to a second prescribed elevation differential slightly below the horizon. Although the feed horn causes a partial blockage of rays reflected by the shaped subreflector directly beneath the antenna, reduction in nadir gain is quite tolerable in a UAV application, as it lasts for only a fraction of second when the UAV platform passes directly over the ground station, where range-based propagation loss is minimum. Also, as the principal theater of deployment of a UAV is geographically remote from the ground station, nadir-associated gain reduction is not a practical problem.

Claims

1. A method of providing a communication link between a first site and a second site comprising the steps of:

(a) coupling communication equipment at said first site with a feed element for an antenna structure employed at said first site; and

(b) configuring said antenna structure as a ring focus subreflector formed as a shaped ellipsoid that is exclusive of an associated main reflector, said ring focus subreflector being operative to direct RF energy emanating from said feed element in a generally hemispherical radiation pattern that encompasses the horizon and a region along a boresight of said antenna structure that includes said second site.

2. A method according to claim 1, wherein said ring focus subreflector is configured such that said radiation pattern has a peak gain in the vicinity of the horizon.

3. A method according to claim 1, wherein said ring focus subreflector is configured such that said radiation pattern has a peak gain within a prescribed elevation range above and below the horizon.

4. A method according to claim 1, wherein said radiation pattern has a reduced gain in the nadir direction.

5. A method according to claim 1, wherein said first site comprises an unmanned aerial vehicle.

6. A method according to claim 1, wherein said first site comprises an aerial communications platform and said second site comprises a ground station, and wherein step (a) comprises coupling communication equipment of said aerial communications platform with said feed element for said ring focus antenna structure that is carried by said aerial communications platform, and step (b) comprises arranging said ring focus subref lector to direct said RF energy emanating from said feed element in a generally hemispherical radiation pattern that encompasses the horizon and a terrestrial region beneath said aerial communications platform that includes said ground station.

7. A method of providing a communication link between a first communications location and a second communications location comprising the steps of:

(a) coupling communication equipment of said first communications location with a feed element for an antenna structure; and

(b) providing said antenna structure as a shaped ellipsoid subreflector of a ring focus antenna that is rotationally symmetric about an axis of said feed element, and is configured to direct RF energy emanating from said feed element in a generally hemispherical radiation pattern that exhibits a maximum gain over a peak gain region extending from a first prescribed elevation differential slightly above the horizon to a second prescribed elevation differential slightly below the horizon, and encompassing said second communications location.

8. A method according to claim 7, wherein said first location corresponds to an aerial communications platform and said second location corresponds to a ground station.

9. A method according to claim 7, wherein said radiation pattern has a reduced gain in the nadir direction.

10. An antenna of the type employed for air-to-ground link hemispherical communication coverage comprising an ellipsoid shaped ring focus type subreflector, that is rotationally symmetric about a boresight axis of a feed horn to which communication equipment on board an aerial vehicle is coupled, and being exclusive of an associated main reflector that may otherwise intercept rays emanating from said subreflector in a generally hemispherical pattern, said generally hemispherical radiation pattern extending toward the horizon and encompassing a ground station, and wherein said subreflector is shaped such that said hemispherical radiation pattern has a peak gain profile that extends from a first prescribed elevation differential slightly above the horizon to a second prescribed elevation differential slightly below the horizon.

11. An antenna for providing a communication link between a first location and a second location remote with respect to said first location, said antenna comprising an RF energy feed element to which communication equipment of said first communications location is coupled, and a shaped ring focus subreflector that is rotationally symmetric about an axis of said feed element, and shaped as a non-regular conical surface of revolution, and being configured to project RF energy directed thereon from said feed element in a generally hemispherical radiation pattern, exclusive of a main reflector, said generally hemispherical radiation pattern exhibiting peak gain toward the horizon and encompassing said second communications location.

12. An antenna according to claim 11, wherein said first location corresponds to an aerial communications platform and said second location corresponds to a ground station.

13. An antenna according to claim 11, wherein said generally hemispherical radiation pattern exhibits peak gain in a peak gain region that extends from a first prescribed elevation differential slightly above the horizon to a second prescribed elevation differential slightly below the horizon.

14. An antenna according to claim 11, wherein said shaped subreflector comprises a shaped ellipsoid subreflector of a ring focus antenna.

15. An antenna according to claim 11, wherein said radiation pattern has a reduced gain in the nadir direction.

16. An antenna according to claim 11, wherein said feed element is adjacent to a vertex to said ring focus subreflector on a boresight axis of said antenna.

17. An antenna according to claim 11, wherein said feed element has a feed aperture thereof located a distance on the order of two to three wavelengths of the frequency of operation of said antenna from a vertex of said subreflector.