Planar array antenna

• US 20030122724A1
• Filed: 12/24/2002
• Published: 07/03/2003
• Est. Priority Date: 04/18/2000
• Status: Abandoned Application

• Current Assignee: ERA Patents Limited
• Original Assignee: ERA Patents Limited
• Inventors: Shelley, Martin William, Sanchez, Francisco Javier Vazquez
• Application Number:
  US10/257,627
• Publication Number:
  US 20030122724A1
• Time in Patent Office: Days
• US Class Current: 343/786
• CPC Class Codes: H01Q 1/525 between emitting and receiving antennas
• CPC Class Codes: H01Q 21/0081 using suspended striplines
• CPC Class Codes: H01Q 21/064 using horn or slot aerials slotted waveguides arrays H01Q21/005
• CPC Class Codes: H01Q 5/55 for horn or waveguide antennas

Abstract

A flat plate or slab antenna (1) is fabricated from a number of sandwiched layers in which a number of arrayed individual antenna elements (3) are formed. The antenna elements (3) each include a horn (12) with a rectangular aperture (13) feeding (or fed by) individual rectangular waveguides (15). Two orthogonal probes (17,20) protrude into each waveguide (13), each of which is connected to respective beamforming networks. The network of first probes (17) operates at a first frequency while the network of second probes (20) operates at a frequency which is different from the first frequency. In the preferred embodiment, the edges (13) of the horn apertures (12) are parallel to the sides (6, 7, 8, 9) of the antenna slab while the walls of the rectangular waveguides are at 45° to the sides (6, 7, 8, 9) of the slab. The antenna (1) is able to receive and/or transmit two orthogonally linearly polarised signal at different frequencies and is therefore capable of full duplex operation. Various additional features are also described which reduce coupling between the first (17) and second (20) probes, improve isolation between receiving and transmitting sections and maximise power dissipation within the structure.

Claims

1. An antenna element (3) comprising:

a horn (12) having a central cavity and edges (13) defining a substantially rectangular shaped aperture,

a substantially rectangular waveguide (15) coaxial with and having an opening connected to the central cavity of the horn (12),

a first probe (17) provided within the rectangular waveguide (15) for transmitting and/or receiving a first signal linearly polarised in a first direction, and

a second probe (20) provided within the rectangular waveguide (15) for transmitting and/or receiving a second signal linearly polarised in a second direction,

wherein the first and second signals have different operating frequencies, the first and second directions are orthogonal and the edges (13) of the horn aperture (12) are at an angle of 45°

to the directions of polarisation of the first and second signals.

2. An antenna element (3) as claimed in claim 1, wherein the central cavity of the horn (12) is stepped from the horn aperture (13) to the opening of the rectangular waveguide (15).

3. An antenna element (3) as claimed in claim 1, wherein the central cavity of the horn (12) tapers from the horn aperture (13) to the opening of the rectangular waveguide (15).

4. An antenna element (3) as claimed in any one of the preceding claims, wherein the first (17) and second (20) probes are balanced and connected to input/output sockets (31) of a “

T”

power divider or a 180°

hybrid coupler.

5. A planar array antenna (1) comprising:

an antenna having a number of antenna elements (3) as claimed in any one of the preceding claims arranged so that the directions of polarisation of the first and second signals associated with each antenna element (3) are aligned respectively with the polarisation directions of the first and second signals of each of the other antenna elements (3), and

first and second beam forming networks which include the first (17) and second (20) probes respectively.

6. A planar array antenna (1) as claimed in claim 5, comprising a slab having front (4) and rear (5) substantially parallel planar surfaces and two pairs of substantially parallel side walls (6,7,8,9), the antenna elements (3) arranged with their horn apertures (12) formed in the front surface (4) so that each of the edges (13) of the horn apertures (12) are parallel with one or other of the pairs of side walls (6,7,8,9) of the antenna slab (1),

a heat conducting plate (23) forming the rear surface (5) of the antenna slab, at least part of the waveguides (15) of the antenna elements (3) protruding from the heat conducting plate (23), the heat conducting plate (23) forming a surface of cavities (22) in the antenna slab between the waveguides (12) of adjacent antenna elements (3) and,

wherein at least one heat producing electronic component (29) in the signal path of the planar array antenna (1) is placed in thermal contact with the heat conducting plate (23) which acts as a heat sink.

7. A planar array antenna (1) as claimed in claim 6, wherein cooling fins (24) are attached to the heat conducting plate (23), the cooling fins (24) projecting into at least some of the cavities (22) formed between the waveguides (12) of adjacent antenna elements (3).

8. A planar array antenna (1) as claimed in any one of claims 5 to 7, wherein at least parts of the first and second beam forming networks are formed from suspended strip line filter structures.

9. A planar array antenna (1) as claimed in any one of claims 5 to 8, wherein first and second electrical connectors (31) are provided on or adjacent to the rear surface (5) of the antenna slab to conduct the first and second signals respectively, wherein the first and second electrical connectors (31) are respectively connected to the first and second beam forming networks by first and second co-axial filters (34).

10. A planar array antenna (1) as claimed in any one of claims 5 to 9, wherein one of said first or second beam forming networks is a transmit only beam forming network and wherein a plurality of electrical connectors (31) are provided at or near the rear surface (5) of the antenna slab which are connected to said transmit only beam forming network by co-axial filters (34), each of which has an associated amplifier (29) connected thereto and in thermal contact with said heat conducting plate (23).