Communications: radio wave antennas – Antennas – With housing or protective covering
Reexamination Certificate
1999-10-29
2002-09-17
Phan, Tho (Department: 2821)
Communications: radio wave antennas
Antennas
With housing or protective covering
C343S7000MS
Reexamination Certificate
active
06452565
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
Not applicable
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable
REFERENCE TO A “MICROFICHE APPENDIX”
Not applicable
FIELD OF THE INVENTION
This invention relates to dielectric resonator antennas with steerable receive and transmit beams and more particularly to an antenna having several separate feeds such that several separate beams can be created simultaneously and combined as desired.
BACKGROUND OF THE INVENTION
Since the first systematic study of dielectric resonator antennas (DRAs) in 1983 (LONG, S. A., McALLISTER, M. W., and SHEN, L. C.: ‘The resonant cylindrical dielectric cavity antenna’, IEEE Trans. Antennas Propagat., AP-
3
1, 1983, pp 406-412), interest has grown in their radiation patterns because of their high radiation efficiency, good match to most commonly used transmission lines and their small physical size (MONGIA, R. K. and BHARTIA, P.: ‘Dielectric resonator antennas—A review and general design relations for resonant frequency and bandwidth’, Int. J. Microwave & Millimetre Wave Computer-Aided Engineering, 1994, 4, (3), pp 230-247). Most configurations reported have used a slab of dielectric material mounted on a ground plane excited by either an aperture feed in the ground plane or by a probe inserted into the dielectric material. A few publications have reported on experiments using two probes fed simultaneously in a circular dielectric slab. These probes were installed on radials at 90° to each other and fed in anti-phase so as to create circular polarisation (MONGIA, R. K., ITTIPIBOON, A., CUHACI, M. and ROSCOE D.: ‘Circular polarised dielectric resonator antenna’, Electron. Lett., 1994, 30, (17), pp 1361-1362; and DROSSOS, G., WU, Z. and DAVIS, L. E.: ‘Circular polarised cylindrical dielectric resonator antenna’, Electron. Lett., 1996, 32, (4), pp 281-283.3, 4) and one publication included the concept of switching probes on and off (DROSSOS, G., WU, Z. and DAVIS, L. E.: ‘Switchable cylindrical dielectric resonator antenna’, Electron. Lett., 1996, 32, (10), pp
862-864).
All references mentioned herein are incorporated herein by reference:
SUMMARY OF THE PRESENT INVENTION
The present invention seeks to provide a DRA having several probes or aperture feeds connected in such a way that the antenna pattern can be steered, and also the use of two probes driven simultaneously in-phase and 180° out of phase in order to generate monopulse sum and difference patterns.
One method of electronically steering an antenna pattern is to have a number of existing beams and to switch between them, or to combine them so as to achieve the desired beam direction. A circular DRA may be fed by a single probe or aperture placed in or under the dielectric and tuned to excite a particular resonant mode. In preferred embodiments, the fundamental HEM
11&dgr;
mode is used, but there are many other resonant modes which produce beams that can be steered equally well using the apparatus of embodiments of the present invention. The preferred HEM
11&dgr;
mode is a hybrid electromagnetic resonance mode radiating like a horizontal magnetic dipole and giving rise to vertically polarised cosine or figure-of-eight shaped radiation pattern (LONG, S. A., McALLISTER, M. W., and SHEN, L. C.: ‘The resonant cylindrical dielectric cavity antenna’, IEEE Trans. Antennas Propagat., AP-31, 1983, pp 406-412). Modelling by the present Inventors of cylindrical DRAs by FDTD (Finite Difference Time Domain) and practical experimentation has shown that if several such probes are inserted into the dielectric and one is driven whilst all the others are open-circuit then the beam direction can be moved by switching different probes in and out. Furthermore, by combining feeds in different ways, sum and difference patterns can be produced which allow continuous beam-steering and direction finding by amplitude-comparison, monopulse or similar techniques.
Many of these results are described in the paper KINGSLEY, S. P. and O'KEEFE, S. G., “Beam steering and monopulse processing of probe-fed dielectric resonator antennas”, IEE proceedings—Radar Sonar and Navigation, 146, 3, 121-125, 1999, the disclosure of which is incorporated into the present application by reference.
It has been noted by the present inventors that the results described in the above reference apply equally to DRAs operating at any of a wide range of frequencies, for example from 1 MHz to 100,000 MHz and even higher for optical DRAs. The higher the frequency in question, the smaller the size of the DRA, but the general beam patterns achieved by the probe/aperture geometries described hereinafter remain generally the same throughout any given frequency range. Operation at frequencies substantially below 1 MHz is possible too, using dielectric materials with a high dielectric constant.
According to a first aspect of the present invention, there is provided a dielectric resonator antenna including a grounded substrate, a dielectric resonator disposed on the grounded substrate and a plurality of feeds for transferring energy into and from different regions of the dielectric resonator, the feeds being activatable individually or in combination so as to produce at least one incrementally or continuously steerable beam which may be steered through a predetermined angle.
According to a second aspect of the present invention, there is provided a dielectric resonator antenna system including a grounded substrate, a dielectric resonator disposed on the grounded substrate, a plurality of feeds for transferring energy into and from different regions of the dielectric resonator, and electronic circuitry adapted to activate the feeds individually or in combination so as to produce at least one incrementally or continuously steerable beam which may be steered through a predetermined angle.
Advantageously, the antenna and antenna system of the present invention are adapted to produce at least one incrementally or continuously steerable beam which may be steered through a complete 360 degree circle.
Advantageously, there is additionally or alternatively provided electronic circuitry to combine the feeds to form sum and difference patterns to permit radio direction finding capability of up to 360 degrees.
The electronic circuitry may additionally or alternatively be adapted to combine the feeds to form amplitude or phase comparison radio direction finding capability of up to 360 degrees.
Preferably, radio direction finding capability is a complete 360 degree circle.
The feeds may take the form of conductive probes which are contained within or placed against the dielectric resonator or may comprise aperture feeds provided in the grounded substrate. Aperture feeds are discontinuities (generally rectangular in shape) in the grounded substrate underneath the dielectric material and are generally excited by passing a microstrip transmission line beneath them. The microstrip transmission line is usually printed on the underside of the substrate. Where the feeds take the form of probes, these may be generally elongate in form. Examples of useful probes include thin cylindrical wires which are generally parallel to a longitudinal axis of the dielectric resonator. Other probe shapes that might be used (and have been tested) include fat cylinders, non-circular cross sections, thin generally vertical plates and even thin generally vertical wires with conducting ‘hats’ on top (like toadstools). Probes may also comprise metallized strips placed within or against the dielectric. In general any conducting element within or against the dielectric resonator will excite resonance if positioned sized and fed correctly. The different probe shapes give rise to different bandwidths of resonance and may be disposed in various positions and orientations (at different distances along a radius from the center and at different angles from the center, as viewed from above) within or against the dielectric resonator so as to suit particular circumstances. Furthermore, there may be provided probes within or against the
Kingsley Simon P.
O'Keefe Steven G.
antenova Limited
Dinh Trinh Vo
Garvey, Smith, Nehrbass & Doody, L.L.C.
Nehrbass Seth M.
Phan Tho
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