Geodesic dome-lens antenna

• US 4,488,156 A
• Filed: 02/10/1982
• Issued: 12/11/1984
• Est. Priority Date: 02/10/1982
• Status: Expired due to Term

• Current Assignee: Hughes Aircraft Company (Rtx Corporation)
• Original Assignee: Hughes Aircraft Company (Rtx Corporation)
• Inventors: Uyeda, Harold A., DuFort, Edward C.
• Primary Examiner(s): Lieberman, Eli
• Assistant Examiner(s): Wimer, Michael C.
• Application Number:
  US06/347,666
• Time in Patent Office: 1,035 Days
• Field of Search: 343/911 R, 343/911 L, 343/754, 343/783, 343/753, 343/772, 343/780, 343/786, 343/909
• US Class Current: 343/754
• CPC Class Codes: H01Q 15/04 comprising wave-guiding channel or channels bounded by effective conductive surfaces substantially perpendicular to the electric vector of the wave, e.g. parallel-plate waveguide lens
• CPC Class Codes: H01Q 19/062 for focusing
• CPC Class Codes: H01Q 3/245 in the focal plane of a focussing device

Abstract

An antenna of the geodesic lens type is disclosed. The antenna structure is based on optical principles and provides wide angle scanning of a narrow base. The exact shape of the domed structure is found by solving an integral equation and results in nearly perfect focus in the scan plane. A dielectric loaded flared horn is attached to the feed circle of the domed structure and focusses energy in the plane orthogonal to the scan plane. The cross sectional shape of the outer curvature of the dielectric is elliptical. Since the structure is circularly symmetrical, constant beam shape, wide angle scanning, and a rapid scan rate are possible.

Claims

1. An antenna for providing a substantially collimated beam, comprising:

(a) a geodesic lens antenna having two concentric surfaces of revolution about a central axis

(b) feed means for feeding energy into and out of the area between the surfaces of revolution;

(c) an annular flared horn having a first annular conductor coupled to one concentric surface at the periphery thereof and having a second annular conductor coupled to the second concentric surface at the periphery thereof, the annular conductors disposed at a predetermined angle to each other;

(d) an annular dielectric lens disposed between the annular conductors and having, in a plane parallel with the central axis, a cross-sectional shape of a wedge with the tip of the wedge facing towards the central axis, and having an outer surface facing away from the central axis; and

(e) the geodesic lens antenna further being shaped to compensate for the presence of the annular dielectric lens to maintain the collimation of energy which propagates from the feed means through the geodesic lens antenna and through the dielectric lens, in a plane perpendicular to the central axis;

(f) whereby the beam is substantially collimated in two perpendicular planes.

3. The structure of claim 1 wherein the geodesic lens antenna is a full figure of revolution about the central axis.

4. The structure of claim 1 wherein the shape of the energy transmission path through the geodesic lens antenna is in accordance with:

##EQU22## where v=b or aη

_o or bη

_o

where;

z(ρ

)=surface of revolution about the central axis through the geodesic lens antenna

η

_o =refractive index of the dielectric lens

a=radius of the geodesic lens antenna periphery

b=radius of the antenna including the dielectric lens

η

=distance from the central axis to the surface of revolution of the energy transmission path through the geodesic lens antenna.

5. The structure of claim 1 wherein the dielectric lens has a cross sectional shape in accordance ##EQU23## where:

η

=distance from the central axis of the geodesic lens antenna to the outer outer surface of the dielectric lens

η

_o =refractive index of the dielectric lens

a=radius of the geodesic lens antenna

b=radius of the antenna including the dielectric lens

Z=the distance to the outer surface of the dielectric lens from a line bisecting the dielectric lens.

6. The structure of claim 1 wherein the dielectric lens has a refractive index of less than 1.

7. The antenna of claim 1 wherein the cross-sectional shape of the outer surface of the dielectric lens is elliptical.

2. The structure of claim 2 wherein:

(a) the two concentric surfaces are separated from each other by a distance that is less than one-half wavelength at the highest frequency of operation;

(b) whereby the TEM mode may exist between the two concentric surfaces.

8. An antenna for providing a substantially collimated beam comprising:

(a) a geodesic lens antenna having two concentric surfaces of revolution about a central axis;

(b) lens means coupled to the geodesic lens antenna for refracting energy along a predetermined length of the periphery of the concentric surfaces to form a collimated beam in a plane parallel to the central axis, the lens means comprising an annular flared horn having a first annular conductor coupled to one of the concentric surfaces at the periphery thereof and having a second annular conductor coupled to the second concentric surface at the periphery thereof, the annular conductors disposed at a predetermined angle to each other, and the lens means further comprising an annular dielectric lens disposed between the annular conductors and, in a plane parallel with the central axis, having a cross-sectional shape of a wedge with the tip of the wedge facing towards the central axis and having an outer surface facing away from the central axis; and

(c) the geodesic lens antenna further being shaped such that it compensates for the refraction by the lens means to maintain collimation of the beam in a plane perpendicular to the central axis;

whereby a beam is provided which is substantially collimated in two perpendicular planes.

9. The antenna of claim 8 wherein the shape of the outer surface of the dielectric lens is elliptical.

10. An antenna for providing a substantially collimated beam, comprising:

(a) an annular dielectric lens apparatus comprising an annular flared horn having two annular conductors disposed at a predetermined angle to each other and an annular dielectric lens disposed between the annular conductors and having a cross-sectional shape of a wedge with the tip of the wedge facing the direction of convergence of the annular conductors, and having an outer surface opposite the tip, shaped for collimating a beam in the plane of the cross-section; and

(b) a geodesic lens antenna having two concentric conductors which are surfaces of revolution about a central axis coupled at their peripheries to respective annular conductors such that the wedge shaped cross-section of the dielectric lens is in a plane parallel to the central axis, the geodesic lens antenna further being shaped to compensate for the presence of the annular dielectric lens apparatus to maintain collimation of the energy which propagates through the geodesic lens antenna and the lens apparatus from a point on the periphery of the geodesic lens antenna in a plane perpendicular to the central axis;

whereby the beam is substantially collimated in two perpendicular planes.

11. The antenna of claim 10 wherein the cross-sectional shape of the outer surface of the dielectric lens is elliptical.