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Title:
MICROWAVE ANTENNAS
Document Type and Number:
WIPO Patent Application WO/2002/097919
Kind Code:
A1
Abstract:
There is described an antenna assembly made up of a number of separate antenna elements. Each element is a substantially planar array having a length substantially greater than its width. The elements are mounted with their co-axes parallel for tilting movement with respect to the horizontal. The assembly is mounted in the housing which can rotate in a horizontal plane.

Inventors:
COLLINS JOHN LOUIS FREDERICK C (GB)
Application Number:
PCT/GB2002/002272
Publication Date:
December 05, 2002
Filing Date:
May 31, 2002
Export Citation:
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Assignee:
FORTEL TECHNOLOGIES INC (US)
COLLINS JOHN LOUIS FREDERICK C (GB)
International Classes:
H01Q3/04; H01Q3/08; H01Q21/06; H01Q25/00; (IPC1-7): H01Q3/04; H01Q3/08; H01Q25/00
Domestic Patent References:
WO2001011718A12001-02-15
Foreign References:
EP0920072A21999-06-02
EP0487464A21992-05-27
Other References:
ITO Y ET AL: "A MOBILE 12 GHZ DBS TELEVISION RECEIVING SYSTEM", IEEE TRANSACTIONS ON BROADCASTING, IEEE INC. NEW YORK, US, vol. 35, no. 1, 1 March 1989 (1989-03-01), pages 56 - 61, XP000039310, ISSN: 0018-9316
PATENT ABSTRACTS OF JAPAN vol. 016, no. 038 (E - 1161) 30 January 1992 (1992-01-30)
Attorney, Agent or Firm:
MURGITROYD & COMPANY (Scotland House 165-169 Scotland Street Glasgow G5 8PL, GB)
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Claims:
CLAIMS
1. 1 An antenna assembly comprising at least two antenna elements, each of the antenna elements comprising a substantially planar array which has a length substantially greater than its width, the antenna elements being mounted with their long axes parallel for tilting movement with respect to the horizontal.
2. An antenna assembly as claimed in Claim 1, wherein the antenna elements are arranged to tilt in unison at a common angle to the horizontal.
3. An antenna assembly as claimed in any preceding claim, wherein the antenna elements are contained within a single housing.
4. An antenna assembly as claimed in any preceding claim, wherein the housing is rotatable in a horizontal plane.
5. An antenna assembly as claimed in any preceding claim, wherein the antenna elements are rotated within the housing about a common vertical axis.
Description:
"Microwave Antennas" The present invention relates to microwave antennas such as those suitable for the reception of television, positional and communication signals from satellites.

It is known to provide antennas in the form of substantially flat planar arrays, for example in the form of metallised plastics mouldings. It is also known to mount such arrays on the roofs of vehicles, typically in such a manner that the array can be rotated around a vertical axis. However, current vehicle mounted antenna arrangements have poor efficiency since the antenna array is positioned horizontally. It is not acceptable to tilt the antenna to a more efficient receiving angle, since this would increase the height of the antenna assembly to a degree which would be unacceptable for vehicle roof mounting.

An object of the invention is to provide an antenna which overcomes or reduces this problem. It is also an object of the invention to provide an improved antenna suitable for other purposes.

Accordingly, the present invention provides an antenna assembly comprising at least two antenna elements, each of the antenna elements comprising a substantially planar array which has a length substantially greater than its width, the antenna elements being mounted with their long axes parallel for tilting movement with respect to the horizontal.

Preferably, the antenna elements are arranged to tilt in unison at a common angle to the horizontal.

Preferably also, the antenna elements are contained within a single housing. The housing may be rotatable in a horizontal plane, or the antenna elements may be rotated within the housing about a common vertical axis.

Embodiments of the invention will now be described, by way of example only, with reference to the drawings, in which: Fig. 1 is a plan view of an antenna assembly forming a first embodiment of the invention; Fig. 2 is a side view corresponding to Fig. 1; Fig. 3 is an end view corresponding to Fig. 1;

Figs. 4,5 and 6 are views of the first embodiment similar to Figs. 1,2 and 3 respectively but showing the antenna in a different orientation; Fig. 7A is a plan view of a second embodiment in a first orientation; Fig. 8 is an end view corresponding to Fig. 7A; Fig. 9A is a side view corresponding to Fig. 7A; Figs. 7B and 7C are plan views of the second embodiment in second and third orientations; and Figs 9B and 9C are side views corresponding to Figs. 7B and 7C.

Referring to Figs. 1 to 3, a microwave antenna assembly comprises a housing 10 transparent to the radiation of interest. Within the housing 10 are disposed two antenna elements 12. Each of the antenna elements 12 is a generally planar array of cells, in which each cell has a receiving horn coupling to one or more waveguides via elements such as polarisers. The antenna elements 12 are formed from plastic layers which are assembled together and metallised.

Antenna elements of this nature are known; see for example our published International Patent Application W095/23440. The known antennas are generally square, for example 12x12 or 20x20 cells, and designed for fixed mounting oriented orthogonal to the line of sight to the transmitter. In the present embodiment, each antenna element is an array of 20x2 cells, and is mounted by pivot pins 14on its long axis such that the element 12 can be tilted.

Figs. 1 to 3 show the antenna elements 12 tilted at 65°to the horizontal. Figs. 4 to 6 shows the same assembly with the elements 12 tilted at 22° to the horizontal; this is the smallest angle which the present embodiment can assume while still presenting the entire area of the horns to the incoming signal, as further tilting would obscure one element 12 behind the other.

The housing 10 can be mounted for rotation in a horizontal plane. Thus the antenna assembly can be steered in horizontal and vertical rotation for best alignment with a given signal source. Such steering can be achieved manually or automatically, as is known.

Figs. 7 to 9 illustrate a modified embodiment in which the antenna elements 12 are mounted within a generally rectangular housing 20.

It is of course possible to use antenna elements having arrays other than 2x20. Increasing the width will increase the height required for tilting from the horizontal. The maximum height which is acceptable will depend on the application. It is equally possible to use more than two antenna elements tilting in unison.

The invention may be applied to substantially planar antenna elements of other types, for example using stripline printed circuit board technology.

Other modifications and improvements may be made within the scope of the present invention.