Communications: radio wave antennas – Antennas – With means for moving directive antenna for scanning,...
Reexamination Certificate
2000-11-22
2001-12-04
Wong, Don (Department: 2821)
Communications: radio wave antennas
Antennas
With means for moving directive antenna for scanning,...
C343S754000
Reexamination Certificate
active
06326931
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a scanning continuous antenna reflector device, and more exactly to a method and a device providing control of the direction of a main lobe or lobes of a scanning antenna without mechanically moving the antenna.
BACKGROUND
Sometimes it is desirable to be able to quickly change radiation direction of an antenna. In other words the antenna lobe is to be quickly shifted or swept between different directions. The demand regarding time is often such that an arrangement for mechanical motions of the antenna is not feasible.
Today antenna arrays are used which contain elements in which a signal phase at each element may be individually set to achieve a control of the main direction of the antenna lobe. Another technique to achieve a control of a radiation lobe is to utilize what is normally referred to as an “optical phased array”, which includes an adaptable lens which, for instance, is disclosed in a document U.S. Pat. No. 5,212,583. This document describes a device utilizing a single plate of a material presenting ferroelectric properties. The plate is provided with a ground-plane on one side and two orthogonal grids on the other side for radiation lobe control. Both the grids and the ground-plane are made in a transparent material, indium/tin oxide. However, this document only refers to optical systems and does not discuss whether this should work within the microwave range.
Two documents U.S. Pat. Nos. 4,706,094 and 4,636,799 both disclose a ferroelectric block between grids of parallel wires. According to the first document only controlling fields are used across the block, i.e. in the propagation direction of the wave. According to the other document the voltages at the wires are arranged such that the field may adopt arbitrary directions in the plane perpendicular to the wires. In the first document it is pointed out that the “normally” high conductive wires only transmits perpendicular, linear polarization but that they may be replaced by resistive wires being able to transmit also parallel polarization of acceptable loss.
WO,A1,93/10571 demonstrates a development of U.S. Pat. No. 4,636,799 where only fields perpendicular to the wires are used. Here only one layer of wires is needed and the ferroelectric material has been divided into a plurality of blocks such that the grid of wires can be disposed in the middle of the ferroelectric layer.
However it will be noted that, the documents cited above are addressing the use of highly conductive wires and a voltage gradient is then achieved by applying different voltages to the individual wires according to a given pattern. Furthermore the devices described are related to utilizing the ferroelectric material for “electro-optic lenses” which primarily directs the utilization to frequencies corresponding to electromagnetic radiation in the nanometer range.
Therefore there is still a demand for a method and a device, which will operate even at a much lower frequency range.
SUMMARY
The present invention discloses a method and a device for the generation of a surface, the reflection phase gradient or transmission phase gradient of which will be varied by means of a controllable static electric field. The present solution takes into account, instead of mainly the transmissive properties, also the reflection properties of an arrangement comprising a ferroelectric material. Such a reflecting surface may contribute to an entire antenna aperture, a portion of an antenna aperture or an element in a conventional array aperture. The division of the aperture will depend on how many degrees of freedom are desired to be able to be controlled simultaneously. In a general case N lobes and M nulls are to be controlled at the same time. In such a case the surface will preferably be designed as a curved surface, for instance a rotation symmetric parabola, while in other cases the reflector element may be designed just as a plane mirror.
According to the present invention an electromagnetically transparent highly resistive film is applied at both sides of a plate presenting ferroelectric properties. At two opposite edges of these resistive films highly conducting wires are applied and electrically connected along the resistive film. The pairs of highly conductive wires of the two films on the plate presenting the ferroelectric properties are running perpendicular to each other. The first pair of highly conducting wires parallel to the y-axis is connected to a first variable voltage source (U
x
), while the second pair of highly conducting wires parallel to the x-axis is connected to a second variable voltage source (U
y
). In this way a lobe may be steered in the plane X-Z by U
x
and in the plane Y-Z by U
y
. In order to obtain low losses and no change of the controlling E field polarity when sweeping the voltage sources, a bias source of the order several hundreds of volts is applied between the two voltage sources. Another benefit of the present design is that it will operate independent of the polarization of the microwave power to be reflected by the present scanning reflector device.
A method according to the present invention is set forth by the attached independent claim
1
and by the dependent claims
2
to
4
.
Similarly a continuous scanning antenna reflector device according to the method of the present invention is set forth by the attached independent claim
5
and further embodiments are defined in the dependent claims
6
to
10
.
REFERENCES:
patent: 4644363 (1987-02-01), Horn et al.
patent: 5729239 (1998-03-01), Rao
Application for 09/717,066 filed Nov. 22, 2000 corresponding to Swedish Patent Application 9904234-3.
Burns Doane Swecker & Mathis L.L.P.
Clinger James
Telefonaktiebolaget LM Ericsson (publ)
Wong Don
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