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Abstract—The dielectric resonator antenna has been in existence for almost 25 years, and over that time a great deal of research has been conducted that demonstrates its positive attributes as a broad band, efficient radiator with great potential, especially for high frequency applications. Its inherently low loss behavior results both from its lack of conducting materials to eliminate ohmic losses and its absence of a dielectric layer that might otherwise allow energy to be guided away from the desired radiation into space. A chronological history of this class of radiator is presented.

Index Terms—Dielectric resonator antenna, resonant radiating structures, dielectric antennas.

I. INTRODUCTION In the 25 years since its introduction the dielectric resonator antenna (DRA) has only made gradual inroads into practical applications despite a great number of very significant developments. From simple beginnings a great variety of structures have been proposed and investigated. Designs for increased bandwidth, circular polarization, alternate feed systems, varying radiation patterns, and use in arrays have all been demonstrated. Positive attributes of these radiators such as their broadband nature, high efficiency, small size, and stable patterns make them particularly attractive for high frequency applications. As the operation frequency of common communications systems moves higher each year, these antennas have the potential to supplant even the ubiquitous microstrip antenna in popularity and use.

II. DISCOVERY AND EARLY DEVELOPMENT The earliest beginnings of what was to be later called the “dielectric resonator antenna” came out of the University of Houston in the early 1980s. Stuart Long and Liang Shen had been involved in some of the first investigations of printed circuit radiators and had concentrated their beginning efforts on the circular microstrip antenna in work sponsored by the US Army Research Office. From the beginning it was recognized that microstrip antennas became less efficient at higher frequencies due to both higher ohmic losses and to increased amounts of power being coupled into surface waves supported by their finite dielectric substrates. At the same time in the microwave circuits community cylindrical dielectric resonators were being used for energy storage devices, but difficulties were being reported owing to the leaky nature of the devices. To take advantage of the radiation being “leaked” from the dielectric resonator, an investigation was begun on a radiator fashioned after both the resonator and the circular microstrip, with both the conducting patch and the dielectric substrate eliminated to reduce both sources of loss and the ultimate design chosen to enhance the radiated fields.

About this same time Long received a fellowship at the US Army Harry Diamond Laboratory for the summer of 1981, and he proposed to do a feasibility study of this new radiator for his project. Initial theoretical calculations had already been done with the simple assumption of perfectly conducting magnetic walls for the cylindrical geometry. Once there an experimental investigation was undertaken. Existing rods of various dielectric materials were

The History of the Development of the Dielectric Resonator Antenna

Stuart A. Long and Ellen M. O’Connor Department of Electrical and Computer Engineering

University of Houston Houston, TX, 77204-4005 USA

1-4244-0767-2/07/$20.00 ©2007 IEEE 872

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cut into cylindrical pieces, holes drilled to accommodate a coaxial probe feed, the dielectric structure mounted onto a conducting ground plane, and measurements of input impedance and radiation patterns made. The geometry figures from the original paper [1] are shown in Figure 1 and photos of the original DRAs are shown in Figure 2.

Fig. 1 Geometry of cylindrical dielectric antenna [1]

Fig. 2 Original DRAs

These experiments confirmed the theoretical predictions that with the proper choices of dimensions and dielectric constant an efficient antenna could be produced with a maximum radiation direction normal to the ground plane as shown in Figure 3. In addition the impedance bandwidth of the new radiator was found to be much greater than that for a comparable microstrip antenna as illustrated in Figure 4.

When Long returned in fall 1981, a new Ph.D. student, Mark McAllister was just at the stage to begin his research program, so he began a much more systematic investigation of these structures. A number of different materials were tried and the position and length of the feed probe were varied to aid in impedance matching. In addition both rectangular and hemispherical shapes were fabricated and measured. Their geometries are shown in Figures 5 and 6.

Fig. 3 Pattern of cylindrical dielectric antenna with r=8.9; radius-to-height ratio a/d=0.5; and a=0.3 cm [1]

Fig. 4 Measured impedance versus frequency for cylindrical dielectric antenna; r=8.9, a/d=0.5, a=0.3 cm [1]

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The first paper submitted was entitled "The Resonant Cylindrical Dielectric Cavity Antenna” [1], but the second one on the rectangular shape actually came to print first [2]. This second paper was actually the first time the term “dielectric resonator antenna” was used, as the first paper referred to the structure as a dielectric cavity antenna. The third one on the hemispherical shape [3] simply used the term “dielectric antenna”. Subsequent publications [4], however, quickly standardized the name of this class of radiators as “dielectric resonator antennas”, or DRAs for short. Alternate forms of feed structures were shown to be effective by a second student, Roger Kranenburg, with publications concerning microstrip [5] and co-planar waveguide [6] feeds.

Fig. 5 Geometry of rectangular dielectric antenna [2]

III. LATER INVESTIGATIONS In the late 1980s and early 1990s several other investigators spread around the world began researching DRAs, and aided in the popularization of these radiators. The first papers from outside the University of Houston were by Haneishi and his colleagues at Saitama University in Japan [7-9]. Shortly afterwards researchers at the University of Mississippi and at the Communications Research

Centre (CRC) in Ottawa began reporting results. Some of the first papers out of Mississippi were authored by Kishk, Glisson, Kajfiz, Ahn, Eisherbeni, and Junker [10-12], while those from Canada came from Ittpiboon, Mongia, Antar, Barthia, Petosa, Cuhaci, and Roscoe [13-15]. Shortly thereafter a large number of contributions were published by the City University of Hong Kong, led by Leung and Luk [16-17]. Later in the mid 1990s Drossos, Wu, and Davis at Manchester began a series of papers on DRAs [18-19].

Fig. 6 Geometry of hemispherical dielectric antenna [3]

During this decade many aspects of DRAs were investigated. Various shapes and feeding structures were proposed and techniques to provide greater bandwidth, circular polarization, and varying patterns were developed. Numerous analysis methods were reported to aid the designer, and the use of DRAs in arrays was pushed forward.

IV. SUMMARY AND CONCLUSIONS With the advent of many new communications

applications which operate at higher and higher frequencies the dielectric resonator antenna would seemingly be poised for a much more significant role as a practical radiator. The main impediment at this time seems to be its more complicated fabrication and resultant higher cost. Once new

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manufacturing techniques are developed for smaller versions of these antennas appropriate for very high frequency operations, their use should become much more widespread.

ACKNOWLEDGMENT

The authors would like to express their gratitude to the many investigators who have contributed to the development of the dielectric resonator antennas.

REFERENCES

[1] S.A. Long, M.W. McAllister and L.C. Shen, "The Resonant Cylindrical Dielectric Cavity Antenna," IEEE Trans. Antennas Propagat.,vol. AP-31, pp. 406-412, May 1983.

[2] M.W. McAllister, S.A. Long, and G.L. Conway, "Rectangular Dielectric Resonator Antenna," Electron. Lett., vol. 19, pp. 218-219, March 1983.

[3] M.W. McAllister and S.A. Long, "Resonant Hemispherical Dielectric Antenna," Electron. Lett., vol. 20, pp. 657-659, Aug. 1984.

[4] S.A. Long and M.W. McAllister, "The Input Impedance of the Dielectric Resonator Antenna," Int. J. Infrared Millimeter Waves, vol. 7, no. 4, pp. 555-570, 1986.

[5] R. Kranenburg and S.A. Long, "Microstrip Transmission Line Excitation of Dielectric Resonator Antennas," Electron. Lett., vol. 24, pp. 1156-1157, Sept 1988

[6] R.A. Kranenburg, S.A. Long, and J.T. Williams, "Coplanar Waveguide Excitation of Dielectric Resonator Antennas," IEEE Trans. Antennas Propagat, vol. AP-39, pp. 119-122, Jan. 1991

[7] M. Haneishi, H. Takazawa, and T. Aoki, "Planar array composed of dielectric resonator antennas," Trans. of the Inst. of Electronics and Communication Engineers of Japan, Part B, vol. J67B, pp. 1486-1487, Dec. 1984.

[8] M. Haneishi and H. Aoyagi, "A consideration of mutual coupling between dielectric resonator antennas," Trans. of the Inst. of Electronics, Information and Communication Engineers B, vol. J70B, pp. 170-171, Jan. 1987.

[9] M. Haneishi and H. Takazawa, "Broadband circularly polarised planar array composed of a pair of dielectric resonator antennas," Electron. Lett., vol. 21, pp. 437-438, May 1985.

[10]A. A. Kishk, H. A. Auda, and B. C. Ahn, "Accurate prediction of radiation patterns of dielectric resonator antennas," Electron. Lett., vol. 23, pp. 1374-1375, Dec. 1987.

[11]A. A. Kishk, B. Ahn, and D. Kajfez, "Broadband stacked dielectric resonator antennas," Electron. Lett., vol. 25, pp. 1232-1233, Aug. 1989.

[12]A. A. Kishk and A. Z. Elsherbeni, "Radiation characteristics of dielectric resonator antennas loaded with a beam-forming ring," AEU, Electronics and Communication, vol. 43, pp. 158-165, May-June 1989.

[13]R. K. Mongia, "Half-split dielectric resonator placed on metallic plane for antenna applications," Electron. Lett., vol. 25, pp. 462-464, March 1989.

[14]J. T. H. St. Martin, Y. M. M. Antar, A. A. Kishk, A. Ittipiboon, and M. Cuhaci, "Dielectric resonator antenna using aperture coupling," Electron. Lett., vol. 26, pp. 2015-2016, Nov. 1990.

[15]A. Ittipiboon, R. K. Mongia, Y. M. M. Antar, P. Bhartia, and M. Cuhaci, "Aperture fed rectangular and triangular dielectric resonators for use as magnetic dipole antennas," Electron. Lett., vol. 29, pp. 2001-2002, Nov. 1993.

[16]K. W. Leung, K. M. Luk, and K. Y. A. Lai, "Input impedance of hemispherical dielectric resonator antenna," Electron. Lett., vol. 27, pp. 2259-2260, Nov. 1991.

[17]K. W. Leung, K. M. Luk, K. Y. A. Lai, and D. Lin, "Theory and experiment of a coaxial probe fed hemispherical dielectric resonator antenna,"IEEE Trans. Antennas Propagat., vol. 41, pp. 1390-1398, Oct. 1993.

[18]G. Drossos, Z. Wu, and L. E. Davis, "Switchable cylindrical dielectric resonator antenna," Electron. Lett., vol. 32, pp. 862-864, May 1996.

[19]G. Drossos, Z. Wu, and L. E. Davis, "Theoretical and experimental investigation of cylindrical dielectric resonator antennas," Microwave and Opt. Tech. Lett., vol. 13, pp. 119-123, Oct. 1996.

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