Dual frequency circularly polarized microwave antenna

• US 5,241,321 A
• Filed: 05/15/1992
• Issued: 08/31/1993
• Est. Priority Date: 05/15/1992
• Status: Expired due to Term

• Current Assignee: Space Systems/Loral Incorporated (Loral Space and Communications Incorporated)
• Original Assignee: Space Systems/Loral Incorporated (Loral Space and Communications Incorporated)
• Inventors: Tsao, Chich-Hsing A.
• Primary Examiner(s): Wimer, Michael C.
• Application Number:
  US07/884,512
• Time in Patent Office: 473 Days
• Field of Search: 343/700 MS, 343/846, 343/830, 343/848
• US Class Current: 343/700.0MS
• CPC Class Codes: H01Q 5/364 Creating multiple current paths
• CPC Class Codes: H01Q 9/0435 using two feed points
• CPC Class Codes: H01Q 9/0442 with particular tuning means
• CPC Class Codes: H01Q 9/0457 electromagnetically coupled to the feed line

Abstract

An aperture coupled microwave antenna (10) for processing circularly polarized signals. The antenna (10) comprises a first planar dielectric layer (22) upon which a conductive radiating patch (12) is mounted. Attached to the radiating patch (12) are tuning means (20, 72) for converting linearly polarized signals into circularly polarized signals. The tuning means preferably takes the form of conductive tuning stubs (20). Abutting an opposite face (23) of the first dielectric layer (22) is a conductive ground plane (24) having two orthogonal elongated apertures (26, 28). The radiating patch (12) is electromagnetically coupled, through the two elongated apertures (26, 28), to two input/output ports (48, 56) by two conductive feeding circuits (38, 40). Each of the feeding circuits (38, 40) interacts with only one of the elongated apertures (26, 28, respectively). The two feeding circuits (38, 40) and the elongated apertures (26, 28) are designed to operate in isolation. This allows the antenna (10) of the present invention to simultaneously process two signals having different frequencies.

Claims

1. A microwave antenna comprising

(a) a substantially planar dielectric layer having a top and a bottom face;

(b) a substantially planar conductive radiating patch having a plurality of sides mounted on the top face of the dielectric layer;

(c) a substantially planar conductive ground plane having at least one aperture, abutting the bottom face of the dielectric layer;

(d) tuning means electrically connected to the radiating patch for converting two linearly polarized orthogonal field mode signals into circularly polarized signals and vice versa;

(e) an input/output port; and

(f) feeding means for electromagnetically coupling the port to the radiating patch through a selected portion of the aperture;

wherein the radiating patch is substantially a square having a center, and further having two coplanar diagonal axes passing through the center;

wherein the aperture in the ground plane is an elongated aperture having a midpoint, and the aperture is positioned parallel to one of the diagonal axes of the radiating patch such that the midpoint of the aperture is aligned with the center of the patch along an axis that is perpendicular to both the patch and the ground plane.

2. The microwave antenna of claim 1, wherein the tuning means comprises a plurality of conductive tuning stubs which are attached to and extend from the radiating patch.

3. The microwave antenna of claim 1, wherein the tuning means comprises a plurality of notches cut into the radiating patch.

4. A microwave antenna operable at two different frequencies simultaneously, comprising:

(a) a first substantially planar dielectric layer having a top face and a bottom face;

(b) a substantially planar, square conductive radiating patch mounted on the top face of the dielectric layer, having a center and two coplanar diagonal axes passing through the center;

(c) a first substantially planar conductive ground plane abutting the bottom face of the dielectric layer, having first and second elongated apertures which intersect each other at their respective midpoints and which are positioned orthogonal to each other, the ground plane being positioned such that the midponts of the apertures are aligned with the center of the patch along an axis that is perpendicular to both the patch and the ground plane, and each of the apertures is parallel to one of the diagonal axes of the radiating patch;

(d) tuning means electrically connected to the patch for converting two linearly polarized orthogonal field mode signals into circularly polarized signals and vice versa;

(e) a second substantially planar dielectric layer having a top face contacting the ground plane, and a bottom face; and

(f) a third substantially planar dielectric layer having a top face and a bottom face, with a first conductive planar feed network attached to the top face, and a second conductive planar feed network attached to the bottom face, the top face of the third dielectric layer being attached to the bottom face of the second dielectric layer;

wherein

the first feed network is symmetric about a first center plane which is orthogonal to the ground plane, to the radiating patch, and to the third dielectric layer, and which bisects the first aperture, said first feed network comprising at least two elongated substantially identical parallel conductive microstrip elements positioned equidistant from the first center plane, the microstrip elements being positioned so as to orthogonally intersect a projection of the first aperture onto the plane of the third dielectric layer in at least two distinct locations; and

the second feed network is symmetric about a second center plane which is orthogonal to the ground plane, to the radiating patch, to the third layer, and to the first center plane, and which bisects the second aperture, said second feed network comprising at least two elongated substantially identical parallel conductive microstrip elements positioned equidistant from the second center plane, the microstrip elements being positioned so as to orthogonally intersect a projection of the second aperture onto the plane of the third dielectric layer in at least two distinct locations.

5. The antenna of claim 4, wherein the tuning means comprises a plurality of conductive tuning stubs which are attached to and extend from the radiating patch.

6. The antenna of claim 4, wherein the tuning means comprises a plurality of notches cut into the radiating patch.

7. The antenna of claim 4, further comprising:

a fourth substantially planar dielectric layer having a first face abutting the bottom face of the third dielectric layer, and a second face; and

a second substantially planar conductive ground plane abutting the second face of the fourth dielectric layer.

8. The antenna of claim 7, wherein the tuning means comprises a plurality of conductive tuning stubs which are attached to and extend from the radiating patch.

9. The antenna of claim 7, wherein the tuning means comprises a plurality of notches cut into the radiating patch.