Communications: directive radio wave systems and devices (e.g. – Directive – Including a steerable array
Reexamination Certificate
2002-12-19
2004-07-27
Phan, Dao (Department: 3662)
Communications: directive radio wave systems and devices (e.g.,
Directive
Including a steerable array
C342S372000
Reexamination Certificate
active
06768454
ABSTRACT:
The present invention relates to arrays of dielectric resonator antennas (DRAs) in which the patterns of the individual DRA elements may be electronically steered in synchronism with the array pattern.
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 Transactions on Antennas and Propagation, AP-31, 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 small physical size [MONGIA, R. K. and BHARTIA, P.: “Dielectric Resonator Antennas—A Review and General Design Relations for Resonant Frequency and Bandwidth”, International Journal of Microwave and Millimetre-Wave Computer-Aided Engineering, 1994, 4, (3), pp 230-247].
The majority of configurations reported to date have used a slab of dielectric material mounted on a ground plane excited by either an single aperture feed in the ground plane [ITTIPIBOON, A. MONGIA, R. K., ANTAR, Y. M. M., BHARTIA, P. and CUHACI, M: “Aperture Fed Rectangular and Triangular Dielectric Resonators for use as Magnetic Dipole Antennas”, Electronics Letters, 1993, 29, (23), pp 2001-2002] or by a single probe inserted into the dielectric material [McALLISTER, M. W., LONG, S. A. and CONWAY G. L.: “Rectangular Dielectric Resonator Antenna”, Electronics Letters, 1983, 19, (6), pp 218-219]. Direct excitation by a transmission line has also been reported by some authors [KRANENBURG, R. A. and LONG, S. A.: “Microstrip Transmission Line Excitation of Dielectric Resonator Antennas”, Electronics Letters, 1994, 24, (18), pp 1156-1157].
The concept of using a series of these single feed DRAs to build an antenna array has already been explored. For example, an array of two cylindrical single-feed DRAs has been demonstrated [CHOW, K. Y., LEUNG. K. W., LUK, K. M. AND YUNG, E. K. N.: “Cylindrical dielectric resonator antenna array”, Electronics Letters, 1995, 31, (18), pp 1536-1537] and then extended to a square matrix of four DRAs [LEUNG, K. W., LO, H. Y., LUK, K. M. AND YUNG, E. K. N.: “Two-dimensional cylindrical dielectric resonator antenna array”, Electronics Letters, 1998, 34, (13), pp 1283-1285]. A square matrix of four cross DRAs has also been investigated [PETOSA, A., ITTIPIBOON, A. AND CUHACI. M.: “Array of circular-polarized cross dielectric resonator antennas”, Electronics Letters, 1996, 32, (19), pp 742-1743]. Long linear arrays of single-feed DRAs have also been investigated with feeding by either a dielectric waveguide [BIRAND, M. T. AND GELSTHORPE, R. V.: “Experimental millimetric array using dielectric radiators fed by means of dielectric waveguide”, Electronics Letters, 1983, 17, (18), pp 633-635] or a microstrip [PETOSA. A., MONGIA, R. K., ITTIPIBOON, A. AND WIGHT, J. S.: “Design of microstrip-fed series array of dielectric resonator antennas”, Electronics Letters, 1995, 31, (16), pp 1306-1307]. This last research group have also found a method of improving the bandwidth of microstrip-fed DRA arrays [PETOSA, A., ITTIPIBOON, A., CUHACI, M. AND LAROSE, R.: “Bandwidth improvement for microstrip-fed series array of dielectric resonator antennas”, Electronics Letters, 1996, 32, (7), pp 608-609]. It is important to note that none of these publications have discussed the concept of multi-feed DRAs or the concept of array element steering.
Earlier work by the present inventors [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] shows how several spatially separated feeds can be used to drive a single circular slab of dielectric material so as to produce an antenna with several beams facing in different directions. The simultaneous excitation of several feeds means that the DRA can have electronic beamsteering and direction finding capabilities. This work is also disclosed in the present applicants U.S. patent application Ser. No. 09/431,548 entitled “Steerable-beam multiple-feed dielectric resonator antenna”, the disclosure of which is incorporated into the present application by reference.
The present application extends the previous work of Kingsley and O'Keefe by considering the properties and benefits of arrays composed of many such multi-feed DRAs. A wide range of array geometries is considered.
An antenna array is a collection of (often evenly spaced) simple elements such as monopoles, dipoles, patches, etc. The arrangement of elements to form the array may be linear, 2-D, in a circle, etc. and the shape of 2-D arrays may be rectangular, circular, oval, etc. In an array, each individual element has a broad radiation pattern but when they are combined together, the array as a whole has a much narrower radiation pattern. More importantly, by feeding the elements with different phases or time delays, the array pattern can be steered electronically. This is a most useful facility in radar and communications.
It is important to distinguish between the various radiation patterns referred to in the present application. Firstly, each element of the array has its own notional radiation pattern when considered in isolation. This element pattern may be considered to be analogous to the diffraction pattern of one of the light sources in a Young's slits interference demonstration. Secondly, the array as a whole has a notional radiation pattern, known as the array factor, which is the sum of the idealised isotropic element patterns, and which may be considered to be analogous to the interference pattern in a Young's slits demonstration. Finally, the actual radiation pattern formed by the antenna array, known as the antenna pattern, is the product of the element patterns and the array factor. Each of the element pattern, array factor and antenna pattern may be considered to have a direction in which transmission/reception has a maximum gain, and embodiments of the present invention seek to steer these directions in useful ways.
The radiation patterns of the individual elements of an array are fixed so that when the array factor faces straight ahead (on boresight), the resultant antenna pattern has the benefit of the full gain of each individual element. In fact, the gain of the array is the sum of the gain of the elements. However, when the array factor is steered off boresight, the gain can fall because the array factor is moving outside the pattern of the individual elements. The only time this is not true is when the elements are omnidirectional in the plane of the array (such as monopoles), but as these are usually low gain elements there still remains a problem of low gain overall.
Embodiments of the present invention seek to provide an array of dielectric resonator antenna elements, where each element has several energy feeds connected in such a way that the radiation pattern of each element can be steered. One method of electronically steering an antenna element pattern is to have a number of existing beams and to switch between them or, alternatively, to combine them so as to achieve the desired beam direction. The general concept of deploying a plurality of probes within a single dielectric resonator antenna, as pertaining to a cylindrical geometry, is 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 applicants 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
Kingsley Simon P.
O'Keefe Steven G.
antenova Limited
Phan Dao
Sheridan & Ross P.C.
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