Communications: radio wave antennas – Antennas – With spaced or external radio wave refractor
Patent
1988-01-26
1991-04-30
Wimer, Michael C.
Communications: radio wave antennas
Antennas
With spaced or external radio wave refractor
343757, 343813, 343814, 343815, 343818, 342368, H01Q 2106, H01Q 1930, H01Q 330
Patent
active
050122568
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an antenna consisting of an array of dipole radiating elements. Although, for convenience, much of the description and explanation of the invention will employ terms appropriate to transmission, it will be appreciated that this is only a matter of convenience. Antennae and radiating elements are reciprocal devices and may be used in transmission mode and in reception mode as desired.
BACKGROUND OF THE INVENTION
It is well known to employ an array of elements which are individually not very directional to create an antenna which is highly directional. If the array is linear, the antenna beam is fan-shaped. If the array is two-dimensional, the beam is a pencil beam. The narrowness of the beam and hence the antenna gain are influenced in particular by the number of elements in the array.
Although not limited to any particular application, the invention has been conceived in the context of a particular problem, namely the provision of a receiving antenna for a DBS (direct broadcasting by satellite) receiver. Attention is currently concentrated mainly upon parabolic dish antennae for this purpose. Such antennae are large in all three dimensions and of inelegant appearance: their proliferation in residential areas will seriously degrade the environment. There exists a need for an antenna which does not suffer from these defects and which is also of a more inherently robust construction than a dish antenna with its struts supporting a feed-horn.
An array antenna offers the advantage of a robust construction but for DBS usage it is necessary to achieve a very high gain and make suitable provision for aiming the antenna at the desired geostationary satellite. If this were to be done purely by physical positioning (as with a dish antenna), the advantage of a flat, unobtrusive construction is largely lost. What is required is to be able to mount the antenna flat on a suitable wall or possibly roof surface. Moreover, the superficial dimensions of the antenna must be within reasonable bounds if it is to be possible to find suitable mounting areas, say no more than around 1m on the side or diameter. Nevertheless, it must be possible to pack in a large number of elements to get adequate gain which demands that the elements themselves be compact.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an array antenna such as to meet the requirements outlined above.
According to the invention, there is provided an array antenna, comprising an array of dipoles formed in a microstrip structure having a dielectric layer sandwiched between a groundplane and a radiating conductive pattern, characterised in that each dipole has a plurality of parasitic elements adjacent thereto, all parasitic elements lying with the dipoles in a front plane parallel to the groundplane, so as to squint the main beam of the array.
Each dipole is preferably a folded dipole because the higher impedance of such a dipole facilitates design of a feed network. The parasitic elements could be reflectors but are preferably directors, for reasons explained below.
It will be appreciated that a radiating element formed by a dipole and adjacent parasitic elements will necessarily have an asymmetrical radiation pattern relative to the normal to the groundplane, because the parasitic elements are spaced laterally from the dipole, rather than in the direction of the boresight axis, as is the case with conventional aerials employing parasitic elements. This is not a disadvantage in the array antenna according to the invention.
It is well known that the beam of an array antenna can be steered electrically by adjusting the phases with which the elements of the array are fed--a so-called phased array. Although two-coordinate steering is theoretically possible, only one-coordinate steering is really practicable. In an important development of the invention, the beam of the antenna is aimed in a required look-direction by electrical beam-steering to vary the angle of squint of the beam and rotational adjustmen
REFERENCES:
patent: 2217321 (1940-10-01), Runge et al.
patent: 2409944 (1946-10-01), Loughren
patent: 3214760 (1965-10-01), Yonkers
patent: 3541559 (1970-11-01), Evans
patent: 3587110 (1971-06-01), Woodward
patent: 3599217 (1971-08-01), Grant
patent: 3997900 (1976-12-01), Chin et al.
patent: 4097868 (1978-06-01), Borowick
patent: 4336543 (1982-06-01), Ganz et al.
patent: 4370657 (1983-01-01), Kaloi
patent: 4490723 (1984-12-01), Hardie et al.
patent: 4575728 (1986-03-01), Theobald et al.
patent: 4623893 (1986-11-01), Sabban
patent: 4812855 (1989-03-01), Coe et al.
patent: 4823144 (1989-04-01), Guy
Dubost et al., "Log Periodic Flat Short-Circuited Dipole Array with a Squinted Beam", Electronics Letters, vol. 20, No. 10, May 10, 1984, pp. 411-413.
British Broadcasting Corporation
O'Connell Robert F.
Wimer Michael C.
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