Recent Advances in Dielectric-Resonator Antenna Technology

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Recent Advances in Dielectric-Resonator Antenna Technology j
A. Petosa, A. Ittipibo n, Y. M. MAntar’, D. Roscoe, and M. Cuhaci
Communications Researdh Centre 3701 Carling Ave. PO Box 11490, Station H Ottawa, ON Canada K2H 8S2 Tel: (613) 991-9352 Fax: (613) 990-8360 E-mail: aldo.petosa@crc. oc.ca
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‘Royal Military College f Canada Kingston ON Canada K7K 5LO
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Keywords: Dielectric loajed antennas, dielectric resonator antennas, antenna arrays

new?’ This section is intended to answer these questions by illustrating the salient features of DRAs, and bringing to light some of their advantages. A DRA is a resonant antenna, fabricated from low-loss microwave dielectric material the resonant frequency of which is predominantly a function of size, shape, and material permittivity. The basic rectangular DRA-fed by slot coupling, in this case-is shown in Figure 1. The impedance bandwidth is a function of the material’s permittivity and aspect ratio. For this particular DRA, a 10 dB return-loss bandwidth of 6% is obtained (Figure 2a). Bandwidths of up to 10% can be easily achieved with simple rectangular DRAs, with relative permittivity values of 10 or less. The rectan-

1. Abstract

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This paper features Lome of the recent advances in dielectricresonator antenna techn4logy at the Communications Research Centre. Several novel el+ents are presented that offer significant enhancements to parameders such as impedance bandwidth, circular-polarization bandwidbh, gain, or coupling to various feed structures. Several linear1 and planar arrays are also presented, to of dielectric-resonator antenna elements

2. Introduction

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ver the past seven y ars, the Communications Research Centre (CRC), in clos, collaboration with the Royal Military College (RMC) of Canad , has been pursuing a program to investigate the capabilities of ielectric-resonator antenna (DRA) technology as an alternative t more traditional antennas. Much of the initial work focused on cqaracterizing the basic properties of DRAs for a variety of simple shhpes and feed configurations, to illustrate

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mentation, to demonstrate/ the feasibility of using DRAs in an array environment. This paper’summarizes recent work carried out in this program, focusing o the novel DRA configurations and the

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various arrays that have bben developed.

3. Why DRAs?

Microstrip Feed Line
asked questions by those first hearing they?’ and “What do they offer that’s Figure 1. A basic rectangular DRA fed by a slot-coupled microstrip line.

IEEE Antennas and

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several feeding mechanisms can be used (probes, slots, microstrip lines, dielectric image guides, co-planar lines), making DRAs amenable to integration with various existing technologies;

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various modes can be excited, producing broadside or conicalshaped radiation patterns for different coverage requirements; a wide range of permittivity values can be used (fkom about 6 to loo), allowing the designer to have control over size and bandwidth (i.e., wide bandwidth is achievable using low permittivity, and compact size is achievable with high permittivity); DRAs are not as susceptible to tolerance errors as microstrip antennas, especially at higher frequencies. These features make DRAs very versatile elements, which can be adapted to numerous applications by appropriate choice of the design parameters. Also, as will be shown, many of the techniques used for enhancing microstrip-antenna performance are equally applicable to DRAs. A good overview of the early work on DRAs is given in [51].

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Figure 2a. The return loss of the rectangular DRA.

4. Advances in DRA technology This section features some of the latest developments in DRA technology achieved at the CRC. The research has been divided into two categories: novel DRA elements and array configurations.

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4.1 Novel DRA elements The research carried out on novel DRAs can be categorized into the following groups:
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wide-band; compact; circular polarized; high gain; active.

This section presents some of the research in each of these five categories.

Figure 2b. The normalized H-plane radiation pattern of the rectangular DRA at 10.5 GHz.

4.1.1 Wide-band DRAs For many of the existing and emerging communication applications, wide-band antenna operation is desirable to accommodate the increasing data rates required for services such as videoconferencing, direct digital broadcast, EHF portable satellite communications, local multi-point communications, and indoor wireless. Some of these requirements may be met by existing pnntedantenna technology, but with the added cost and complexity associated with multi-layer configurations required for achieving broad bandwidths. This section presents some novel DRAs of relatively simple design, which have demonstrated wide-band performance, and may serve as suitable antenna candidates for these various applications.

gular DRA radiates like a short horizontal magnetic dipole. The normalized H-plane pattem, at 10.5 GHz, is shown in Figure 2b. The E-plane pattem is, in theory, uniform, but in practice it is strongly influenced by the size and shape of the ground plane on which the DRA is mounted. Although the first reported investigation of DRAs dealt with a linear array [12], most of the initial research focused on the characterization of the performance of individual elements of vanous common shapes [13-50]. This research has demonstrated that DRAs offer several attractive features, including: high radiation efficiency (> 95% ), due to the absence of conductor or surface-wave losses; various shapes of resonators can be used (rectangular, cylindrical, hemispherical, etc.), allowing for flexibility in design;

The notch DRA. Simple rectangular DRAs of low permittivity can offer impedance bandwidths of about 10%. For wider bandwidths, a notched rectangular DRA (as shown in Figure 3) has been reported (patent pending), offering bandwidths of up to 28%

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IEEE Antennas and Propagation Magazine, Vol. 40,No.3, June 1998

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The multi-segment RA. For integration with printed technology, direct coupling be een DRAs to microstrip lines is desirable. In general, to achieve strong coupling, the DRA must be fabricated from high-permitti ,ity materials. However, to operate over

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Figure 4b. The normalized H-pane radiation patterns of the notched rectangular DRA ( Ll = 10 mm and L, = 5 mm).

Figure 3a. A gotched rectangular DRA. Figure 5a. A multi-segment DRA.
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Centre Portion Removed (Notch)

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Figure 3b. A schematic iagram of the notched rectangular DRA shown in Figure 3a.
Permittivities Microstrip Feed Line

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Figure 5b. A schematic diagram of the multi-segment DRA in Figure 5a.

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requency (GHz) Figure 4a. The return lois of the notched rectangular DRA.
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a wide bandwidth, the DRA must have a low dielectric constant. To resolve this conflicting requirement, the multi-segment DRA (MSDRA), shown in Figure 5, has been reported (patent pending) [55, 561. It consists of a rectangular DRA of relatively low permittivity, under which one or more thin segments of higher permittivity are inserted. These inserts serve to transform the impedance of the DRA to that of the microstrip line by concentrating the fields undemeath the DRA, and thus significantly improving the coupling performance. In a practical antenna system, the number of inserts should be minimized, to reduce the complexity of the fabrication process and ultimately the cost. Research has thus focused on developing an MSDRA with a single insert. Figure 6 depicts the return loss of an MSDRA, compared to the simple DRA. Coupling is significantly enhanced by the insert, and the MSDRA achieves bandwidths of up to 20%. The MSDRA is amenable to integration

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with printed technology, and is being used as a wide-band array element in a large low-profile array (Section 4.2). A similar configuration, using cylindrical DRAs, was reported in [57].

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Parasitic DRAs. Wide bandwidth can also be achieved with parasitic DRAs, using a similar technique as with microstrip patches. Figure 7 shows a slot-fed DRA with two parasitic elements. The three DRAs are tuned to different frequencies, and the combined retum-loss performance is shown in Figure 8. The individual resonators have bandwidths of up to 5.8%, but when combined, the three-element antenna exhibits a 17% bandwidth for a 10 dB return loss. This configuration remains quite compact, requiring a single feed with no matching network, and has the

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Figure 6. The return loss of an MSDRA compared to that of the simple rectangular DRA. Grounded Substrate

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Figure 9a. A front view of a short-circuit rectangular DRA.

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Figure 9b. A side view of the short-circuit rectangular DRA in Figure 9a. advantage that each DRA can be individually tuned for either wide-band or multiple-frequency-band operation [58, 591.

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Figure 7a. A top view of a slot-fed DRA with two parasitic elements.

4.1.2 Compact DRAs
Since the volume of the DRA increases by a factor of eight each time the frequency is halved, the use of DRAs at lower frequencies becomes questionable, due to the increase in their dimensions (and thus their weight and cost). The size of the DRAs can be significantly reduced by fabricating them from materials with very

of the slot-fed DRA in Figure 7a.

/€€€Antennas and Propagation Magazine, Vol. 40,No. 3, June 1998

high permittivity [IO]. Tde disadvantage of this approach is the accompanying decrease in bandwidth. An altemative method involves the introduction f a short circuit, as shown in Figure 9. By placing the short circ it at a location of symmetry in the Ean be removed, while still maintaination. Alternatively, placing a short xisting D U will result in a lowering s approach has been investigated for of the resonant freque and with decreases of as much probe-fed rectangular 11. Although, there as 65% of the original bandwidth can be is an accompanying d a compact antenna increased by using an with moderate bandwi

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4.1.3 DRAs for circular pblarization

required in applications such as where depolarization due to

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Figure l l a . The normalized radiation pattern of the cross DRA at 11.2 GHz.

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propagation effects preclude the use of linearly polarized systems. Unless antennas are used that are inherently circular polarized (Le., helices, spirals), there is added complexity in the design required to produce CP radiation. In general, a two-point feed is used, where the feed points are spatially 90" apart, and are fed with equalamplitude signals in phase quadrature. The required power-dividing circuit takes up additional real estate, and increases the insertion loss (thus decreasing radiation efficiency). This added complexity can be avoided by adopting a single-point feed system, which, in the case of microstrip-patch antennas, involves designing a patch with a perturbation to excite dual-orthogonal-mode operation. The disadvantage of the single-point-fed microstrip configurations is that they usually produce narrow CP pattern bandwidths (1 - 2% for 3 dB axial ratios) [62]. For DRAs, on the other hand, single-point-fed configurations have been designed with up to 7% CP bandwidth [63-661. Figure 10 shows two configurations: a quasi-square DRA, and a cross-shaped DRA. Both elements generate similar CP

ating circular polarization: A quasia slot aperture or a probe.

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the cross and quasi-square DRAs have been demonstrated to offer wide-band, wide-beam CP performance, which is difficult (if not impossible) to achieve with a single-point-fed, single-layer microstrip patch.

4.1.4 High-gain DRAs At higher frequencies, conductor and surface-wave losses increase significantly for printed technology. In a large planar array, the majority of losses will occur in the printed feed-distribution network. These losses could be reduced if fewer elements were required in the array. This can be achieved for certain fixed-

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Figure 12a. A DRA-fed cavity element. Cross DRA
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Figure 13. The normalized radiation pattern of the cross-DRA cavity element at 20GHz.
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Figure 14a. A slot-fed rectangular FRA (top view). Applied Magnetic Bias Fields

radiation pattems by exciting two spatially orthogonal TE, modes (which radiate like short horizontal magnetic dipoles) in phase quadrature. Figure 11 shows the radiation pattem and boresight axial ratio versus frequency of a cross DRA, designed at X band. The pattern exhibits a 100" beamwidth over which the axial ratio is less than 3 dl3.For wider CP bandwidths, a dual-point-fed ring DRA has been designed, with about a 12% CP bandwidth [67]. Also, a compact 2 x 2 array has been designed with the cross DRAs fed using sequential rotation, to achieve wideband CP performance (17% for 3 dB axial ratio) [68]. Cross DRAs have also been designed to operate at frequencies of up to 30 GHz [69]. Both 40

Microstrip Feed Line

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Figure 14b. A slot-fed rectangular FRA (side-view cross section).

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DRA

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Figure 17b. A side-view schematic of the multi-layer branchline linear array of MSDRAs in Figure 17a.
Multi-Segment DRAs

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Figure 15. The frequenc shift versus applied magnetic bias of the FRA.

Figure 17c. A top-view schematic of the multi-layer branch-line linear array of MSDRAs in Figure 17a.
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Figure 18. The radiation pattern of the branch-line MSDRA array.

Figure 16. A linear D&4 array fed by a microstrip line.

Figure 17a. A multi-I yer branch-line linear array of MSDRAs.

Figure 19. A seven-element array of cross-DRA cavity elements, designed at 30 GHz.
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IEEE Antennas and Prodagation Magazine, Vol. 40, No. 3,June 1998

beam or limited-scan applications by using high-gain elements. A DRA-fed cavity element, shown in Figure 12, has been developed for high-gain operation at K and Ka bands [69, 701 (patent pending). The antenna consists of a circular cavity machined into a metal block, and is fed by a DRA located at the bottom center of the cavity. The DRA is, in turn, fed by slot coupling from a microstrip line, located under the cavity. A dielectric cover is placed over the cavity, to provide impedance matching to free space. In addition to producing high gain, the cavity was designed for integration with power amplifiers that are attached directly to the metal block, which serves as an excellent heat sink for the amplifiers [71]. The gain of this element is a function of cavity diameter. Using the cross DRA for CP operation, a gain above 13 dB,, has been measured at K band for cavity diameters of two wavelengths. A typical pattern is shown in Figure 13. The cross-DRA-fed cavity is being used in an element for a reflector feed array [88].

parameter that can be varied to adjust the amount of coupling between the line and the DRA. Arrays have been successfully designed with 20 dB Taylor amplitude distributions, and with broadband impedance characteristics [79, 821. There are two disadvantages of the series-fed linear array of DRAs. The first is the scanning of the main beam with frequency (common to all series-fed arrays), which precludes the use of this array in wide-band fixed-beam applications. The second is that, in general, only a small amount of coupling is achievable between the microstrip line and the DRAs. Thus, to make an efficient array, many DRAs are required to maximize radiated power. To overcome these disadvantages, a multi-layer microstrip-branch-line array has been developed, as shown in Figure 17 [84]. The array consists of a microstrip branch line, fed in the center by a slot-coupled microstrip line, located on a second substrate. MSDRAs are placed at the ends of the branches, instead of simple DRAs. This is done since, as shown previously, they have significantly more coupling, and thus higher radiation efficiency can be achieved using only a few elements. To avoid beam squint with frequency, the microstrip branch is center fed. A multi-layer approach was adopted, to allow for the integration of active devices in a large array of parallel branches (described in Section 4.2). By using the second layer, more area is made available for mounting any active devices, and good isolation is provided to prevent any spurious radiation of the devices from interfering with the antenna pattem. The impedances of the various branches can be designed to provide the desired amplitude distribution to the elements. The path lengths of the various branches were chosen to provide equal phase to each element at the design frequency. The branch-line array is a compact structure, which takes up the same amount of area as an endfed series array, making it amenable to integration in a larger planar array. Figure 18 shows the measured pattern of a 10 element MSDRA, designed at C band. The array achieved a peak gain of 15.2 dBi, with a 3 dB gain bandwidth of 17%, and boresight crosspolarization levels on the order of 20 dB below the peak co-polarization levels.

4.1.5 Active DRAs Some of the properties of DRAs can be actively controlled by using low-loss ferrite materials. When unbiased, these ferrite-resonator antennas (FRAs) exhibit similar behavior to DRAs. However, when a dc magnetic bias is applied, the tensor nature of the ferrite permeability is invoked, and various parameters can be controlled electronically. FRAs have been designed that exhibit active frequency tuning and polarization agility [72-751. Figure 14 shows a slot-fed rectangular FRA, designed to operate at 10 GHz in its unbiased state. When a dc magnetic bias is applied, the resonant frequency of the FRA will shift either up or down, depending on the direction of the bias field. Measured results are plotted in Figure 15. Frequency shifts of k8% were obtained for this FRA, but much wider shifts are possible by using ferrite material with higher saturation magnetization. Permanent magnets were used in the lab environment to demonstrate this ability, but in practical applications, electromagnets would be more suitable. FRAs have also been designed with polarization agility [74]. By making use of the tensor nature of the ferrite permeability, the polarization of a circular-disk FRA can be magnetically switched from linear to CP. This may prove useful in applications that would benefit from polarization diversity.

Top View
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DRA Elements

5. Linear and planar arrays Much of the work reported on DRAs has focused on the characterization of single elements. A significant effort has been undertaken at the CRC to investigate the performance of DRAs in an array environment. Numerous linear arrays have been developed and, presently, large low-profile two-dimensional arrays are being designed. Some of the research activities are highlighted in this section

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Branched Microstrip Feed

5.1 Linear arrays Several linear arrays of DRAs have been investigated, including probe-fed DRAs with parasitic elements at L band [61], dielectric image-guide-fed DRAs at K band [76], slot-fed arrays at Q band (40 GHz) [77], and several microstrip-line-fed arrays [78831. Microstrip transmission lines offer a simple, practical method for feeding linear arrays of DRAs. A typical array is shown in Figure 16. This configuration is a series-fed array, with the DRAs spaced a guided wavelength apart for in-phase excitation. The position of the DRAs with respect to the microstrip line is a 42

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Figure 20. A low-profile active phased array of MSDRAs.

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in 16 columns. Amplifiers and digital phase shifters are integrated within the array, which is capable of electronic beam steering in the azimuth plane. The active array pattems for the fixed-beam antenna (which include 15 dB-gain LNAs) are shown in Figure 2 1. A peak active gain of 39 dBi has been achieved, with a 3 dB gain bandwidth of 15%. Work is continuing on these arrays, to integrate four-bit digital phase shifters for electronic beam steering in azimuth.

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6. Summary

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This article has featured some of the recent advances in DRA technology, developed at the CRC. The research has focused on novel DRA elements and arrays to meet the continually increasing challenges posed by emerging communications systems. The work to date has demonstrated the advantages and flexibility of DRAs, which have been shown in several instances to offer superior performance to more-traditional antennas. Although not stressed in this article, a significant amount of attention has been paid to the practical implementation of DRAs, by looking at such factors as the manufacturing of the DRAs in large quantities, the placement and bonding of DRAs onto printed boards in a large array, and the effect of fabrication tolerances. The findings to date have been very encouraging, although a significant amount of work is still required in areas such as long-term environmental effects, as well as in the area of analysis and design. As DRA technology matures, however, it should prove a viable alternative to the more-established antenna candidates, offering the engineer more options to solve potentially challenging problems.

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7 Acknowledgments .
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A significant amount of the research on DRAs reported in this article has been carried out by numerous graduate students, a majority of whom hail from the Royal Military College, in Kingston, but also with representatives from the University of Manitoba, in Winnipeg, and Carleton University, in Ottawa. Their diligent efforts over the years have made a strong impact on the progress of this ongoing investigation, and their contribution has been substantial. Particular acknowledgmentsare due to Richard Larose, from the Department of National Defence, for his significant collaborative efforts in the development of the low-profile phased arrays. Finally, the authors wish to thank Rene Douville, Director of Antennas and Integrated Electronics at the CRC, for lending his enthusiastic support and commitment to the DRA project.

5.2 Planar arrays Work has also DRAs. Early work between slot-fed rect More recent work has

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out on various planar arrays of the effects of mutual coupling s in a 2 x 2 planar array [85-871. on more ambitious designs, includ-

8. References
1. J. St. Martin, Y. M. M. Antar, A. A. Kishk, A. Ittipiboon and M. Cuhaci, “Dielectric Resonator Antenna Using Aperture Coupling,” Electronics Letters, 26,24, Nov. 1990, pp. 2015-2016. 2. J. St. Martin, Y. M. M. Antar, A. A. Kishk, A. Ittipiboon and M. Cuhaci, “Aperture-Coupled Dielectric Resonator Antenna,” 1991 IEEE Intemational Symposium on Antennas and Propagation Digest, London, Ontario, Canada, pp. 1086-89.

with the capability of active low-profile ph ments [89-901. The

beam steering. Figure 20 shows an , consisting of 320 MSDRA eleobtain a low-profile, wide-band

3. A. Ittipiboon, R. K. Mongia, Y. M. M. Antar, P. Bhartia, and M. Cuhaci, “An Integrated Rectangular Dielectric Resonator,” 1993 IEEE Intemational Symposium on Antennas and Propagation Digest, Ann Arbor, Michigan, pp. 604-607.

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4. 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,” Electronics Letters, 29,23, Nov. 1993, pp. 2001-2002. 5. R. K. Mongia, A. Ittipiboon, P. Bhartia, and M. Cuhaci, “Electric Monopole Antenna Using a Dielectric Ring Resonator,” Electronics Letters, 29, 17, Aug. 1993, pp. 1530-1531. 6. R. K. Mongia, A. Ittipiboon, Y. M. M. Antar, P. Bhartia, and M. Cuhaci, “A Half-Split Cylindrical Dielectric Resonator Antenna Using Slot Coupling,” Microwave and Guided Wave Letters, 3, 2, Feb. 1993, pp. 38-39 7. A. Ittipiboon, D. Roscoe, and M. Cuhaci, “A General Field Computation of Dielectric Resonator Antennas,” 1994 IEEE International Symposium on Antennas and Propagation Digest, Seattle, Washington, pp. 760-763. 8. R. K. Mongia, A. Ittipiboon, M. Cuhaci, and D. J. Roscoe, “Radiation Q-Factor of Rectangular Dielectric Resonator Antennas: Theory and Experiment,” 1994 IEEE Intemational Symposium on Antennas and Propagation Digest, Seattle, Washington, pp. 764-767. 9. R. K. Mongia, A. Ittipiboon, and M. Cuhaci, “Measurements of Radiation Efficiency of Dielectric Resonator Antennas,” Microwave and Guided Wave Letters, 4, 3, March 1994, p. 80-82. 10. R. K. Mongia, A. Ittipiboon, and M. Cuhaci, “Low Profile Dielectric Resonator Antennas Using a Very High Permittivity Material,” Electronics Letters, 30, 17, Aug. 1994, pp. 1362-1363. 11. M. G. Keller, M. B. Oliver, D. Roscoe, R. K. Mongia, Y. M. M. Antar, A. Ittipiboon, “Millimeter-Wave Dielectric Resonator Antenna,” 1995 USNCKJRSI National Radio Science Meeting Abstracts, Newport Beach, CA, pp. 69. 12. M. T. Birand, R. V. Gelsthorpe, “Experimental Millimetric Array Using Dielectric Radiators Fed by Means of Dielectric Waveguide,” IEE Electronics Letters, 17, 18, Sept. 81, pp. 633635. 13. S. A. Long, M. W. McAllister, and L. C. Shen, “The Resonant Cylindrical Dielectric Cavity Antenna,” IEEE Transactions on Antennas and Propagation, AP-31,3, 1983, pp. 406-412. 14. M. W. McAllister, S. A. Long, “Rectangular Dielectric-Resonator Antenna,” IEE Electronics Letters, 19, March 1983, pp. 218219. 15. R. DeSmedt, “Correction Due to a Finite Permittivity for a Ring Resonator in Free Space,” IEEE Transactions on Microwave Theory and Techniques, MTT-32, Oct. 1984, pp. 1288-1293. 16. D. Kajfez, A.W. Glisson, J. James, “Computed Mode Field Distribution of Isolated Dielectric Resonators,” IEEE Transactions on Microwave Theory and Techniques, MTT-32, 1984, pp. 16091616. 17. M. McAllister, S. A. Long, “Resonant Hemispherical Dielectric Antenna,” IEE Electronics Letters, 20, Aug. 1984, pp. 657659.

18. M. Tsuji, H. Shigesawa, K. Takiyama, “Analytic and Experimental Investigations on Several Resonant Modes in Open Dielectric Resonators,” IEEE Transactions on Microwave Theory and Techniques, MTT-32, June 1984, pp. 628-633. 19. M. Haneishi, H. Takazawa, “Broadband Circularly Polarised Planar Array Composed of a Pair of Dielectric Resonator Antennas,” IEE Electronics Letters, 21, 10, May 1985, pp. 437-438. 20. R. A. Kranenburg, S. A. Long, “Microstrip Transmission Line Excitation of Dielectric Resonator Antennas,” IEE Electronics Letters, 24, 18, Sept. 1988, pp. 1156-1157. 21. A. A. Kishk, B. Ahn, and D. Kajfez, “Broadband stacked Dielectric-Resonator Antennas,” IEE Electronics Letters, 25, 18, AUg. 1989, pp. 1232-1233. 22. A. A. Kishk, H. A. Auda, B. C. Ahn, “Radiation Characteristics of Cylindrical Resonant Antenna with New Applications,” IEEE Antennas and Propagation Society Newsletter, 31, 1, February 1989, pp. 7-16. 23. R. K. Mongia, “Half-split dielectric resonator placed on metallic plane for antenna applications,” IEE Electronics Letters, 25, 1989, pp. 462-464. 24. R. K. Mongia, “Resonant Frequency of Cylindrical Dielectric Resonator Placed in an MIC Environment,” IEEE Transactions on Microwave Theory and Techniques, MTT-38, June 1990, pp. 802804. 25. R. Kranenberg, S. A. Long, J. T. Williams, “Coplanar Waveguide Excitation of Dielectric-Resonator Antennas,” IEEE Transactions on Antennas and Propagation, AP-39, 1, 1991, pp. 1 19-122. 26. K. W. Leung, K. M. Luk, K. Y. A. Lai, “Input Impedance of a Hemispherical Dielectric Resonator Antenna,” IEE Electronics Letters, 27,24, Nov. 1991, pp. 2259-2260. 27. R. K. Mongia, “On the Accuracy of Approximate Methods for Analyzing Cylindrical Dielectric Resonators,” Microwave Journal, Oct. 1991, pp. 146-150. 28. R. K. Mongia, “Theoretical and Experimental Investigations on Rectangular Dielectric Resonators,” IEE Proceedings Part H, 139, 1, Feb. 1992, pp. 98-104. 29. G. P. Junker, A. A. Kishk, A. W. Glisson, “Numerical analysis of Dielectric Resonator Antennas Excited in Quasi-TE Modes,” IEE Electronics Letters, 29, 1993, pp. 1810-1811. 30. A. A. Kishk, A. Ittipiboon, Y. M. M. Antar, and M. Cuhaci, “Dielectric Resonator Antenna Fed by a Slot in the Ground Plane of a Microstrip Line,” Proceedings o the Eighth International f Conference on Antennas and Propagation, ICAP’93, 1993, Part 1, pp. 540-543. 31. A. A. Kishk, A. Ittipiboon, Y. M. M. Antar and M. Cuhaci, “Dielectric Resonator Antennas Fed by a Slot in the Ground Plane of a Microstrip Line,” IEE Eighth International Conference on Antennas and Propagation, ICAP 1993, UK.

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32. A. A. Kishk, M. Study of a Dielectric

nobi, and D. Kajfez, “A Numerical ntenna Above a Grounded Dielectric

46. G. P. Junker, A. A. Kishk, A. W. Glisson, D. Kajfez, “Effects of Fabrication Imperfections for Ground-Plane-Backed Dielectric Resonator Antennas with Coaxial Excitation,” IEEE Antennas and Propagation Magazine, 37, 1995, pp. 40-47. 47. A. A. Kishk, A. Ittipiboon, Y. Antar and M. Cuhaci, “SlotExcitation of the Dielectric Disk Radiator,” IEEE Transactions on Antennas and Propagation, AP-43,2, Feb. 95, pp. 198-201. 48. K. P. Esselle, “Circularly Polarised Higher-Order Rectangular Dielectric Resonator Antenna,” Electronics Letters, 32, 3, Feb. 1996, pp. 150-151. 49. G. P. Junker, A. A. Kishk, and A. W. Glisson, “Two-Port Analysis of Dielectric Resonator Antennas Excited in TE,, Mode,” Electronics Letters, 32, 7, March 1996, pp. 617-618. 50. Z. Li, C. Wu, and J. Litva, “Adjustable Frequency Dielectric Resonator Antenna,” Electronics Letters, 32, 7 , Feb. 96, pp. 606607. 5 1. R. K. Mongia and P. Bhartia, “Dielectric Resonator AntennasA Review and General Design Relations for Resonant Frequency and Bandwidth,” International Journal of Microwave and Millimeter- Wave Computer-Aided Engineering, 4,3, 1994, pp. 230-247. 52. A. Ittipiboon, A. Petosa, D. Roscoe, and M. Cuhaci, “An Investigation of a Novel Broadband Dielectric Resonator Antenna,” 1996 IEEE International Symposium on Antennas and Propagation Digest, Baltimore, MA, pp. 2038-2041.

Antennas,” IEE Pro

140, 5, Oct. 1993, pp. 336-338.

37. G. P. Junker “Effect of an Air drical Dielectric

hk, A. W. Glisson, and D. Kajfez, the Coaxial Probe Exciting a Cylinntenna,” Electronics Letters, 30, 3,

7, July 1994, pp. 960 53. M. Verplanken and J. Van Bladel, “The Electric Dipole Resonances of Ring Resonators of Very High Permittivity,” IEEE Transactions on Microwave Theovy and Techniques, MTT-24, Feb. 1976, pp. 108-112. 54. M. Verplanken , J. Van Bladel, “The Magnetic-Dipole Resonance of Ring Resonators of Very High Permittivity,” IEEE Transactions on Microwave Theory and Techniques, MTT-27, April 1979, pp. 328-332. 1654. 55. A. Petosa, M. Cuhaci, A. Ittipiboon, N. R. S. Simons, R. Larose, “Microstrip-Fed Stacked Dielectric Resonator Antenna,” Proceedings o the Symposium on Antenna Technology and f Applied Electromagnetics ANTEM-96, 1996, Montreal, Canada, pp. 705-708. 56. N. R. S. Simons, A. Petosa, M. Cuhaci, A. Ittipiboon, R. Siushansian, J. Lovetri, S. Gutschling, “Validation of Transmission Line Matrix, Finite-Integration Technique, and Finite-Difference Time-Domain Simulations of a Multi-Segment Dielectric Resonator Antenna,” Applied Computational Electromagnetic Symposium (ACES-97), Monterey, CA, March 1997. 57. G. P. Junker, A. A. Kishk, D. Kajfez, A. W. Glisson, and J. Guo, “Input Impedance of Microstrip-Slot-Coupled Dielectric Resonator Antennas Mounted on Thin Dielectric Layers,” Znternational Journal of Microwave and mm- Wave Computer Aided Engineering, 6, 3 , May 1996, pp. 174-182.

April 1994, pp. 20-3 1.

44. K. P. Esselle, “ of a Rectangular Di

ite-Difference Time-Domain Analysis Resonator Antenna,” Journal o Elecf

58. Z. Fan, Y. M. M. Antar, A. Ittipiboon, A. Petosa, “Parasitic Coplanar Three-Element Dielectric Resonator Antenna Subarray,” Electronics Letters, 32, 9, April, 1996, pp. 789-790. national Symposium on port Beach, CA, pp. 1998 as and Propagation Digest, New59. Z. Fan, Y . M. M. Antar, “Slot-Coupled DR Antenna for

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Dual-Frequency Operation,” IEEE Transactions on Antennas and Propagation, AP-45,2, Feb. 97, pp. 306-308. 60. M. Cooper, A. Petosa, A. Ittipiboon, J. S. Wight, “Implementing Dielectric Resonator Antennas at L-Band for Communications Applications,” Proceedings Wireless 96 Conference, Calgary , 1996. 61. M. Cooper, A. Petosa, A. Ittipiboon, J. S. Wight, “Investigation of Dielectric Resonator Antennas for L-Band Communications,” Proceedings of the Symposium on Antenna Technology and Applied Electromagnetics ANTEM-96, 1996, Montreal, Canada, pp. 167-170. 62. J. R. James, P. S. Hall (eds.), Handbook of Microstrip Antennas, London, Peter Peregrinus, 1989. 63. A. Ittipiboon, D. Roscoe, R. K. Mongia, and M. Cuhaci, “A Circularly Polarized Dielectric Guide Antenna With A Single Slot Feed,” Proceedings of the Symposium on Antenna Technology and Applied Electromagnetics ANTEM-94, 1994, Ottawa, Canada, pp. 427-430. 64. M. B. Oliver, R. K. Mongia, Y. M. M. Antar, “A New Broadband Circularly Polarized Dielectric Resonator Antenna,” 1995 IEEE Intemational Symposium on Antennas and Propagation Digest, Newport Beach, CA, pp. 738-741. 65. M. B. Oliver, Y . M. M. Antar, R. K. Mongia, and A. Ittipiboon, “Circularly Polarised Rectangular Dielectric Resonator Antenna,” Electronics Letters, 3 5 6 , 1995, pp. 418-419. 66. P. Dombowsky, Y . M. M. Antar, A. Petosa, A. Ittipiboon, “L-Band Circularly Polarized Rectangular Dielectric Resonator Antennas,” International Conference on Electromagnetics in Advanced Applications (ICEAA), 1997, Torino, Italy. 67. R. K. Mongia, A. Ittipiboon, M. Cuhaci, and D. Roscoe, “Circularly Polarized Dielectric Resonator Antenna,” Electronics Letters, 30, 17, Aug. 1994, pp. 1361-1362. 68. A. Petosa, A. Ittipiboon, and M. Cuhaci, “An Array of Circular-Polarised Cross Dielectric Resonator Antennas,” Electronics Letters, 32, 19, Sept. 96, pp. 1742-1743. 69. J. Carrie, N. R. S. Simons, A. Ittipiboon, D. J. Roscoe, A. Sebak, L. Shafai, “A Ka-Band Circularly Polarized Dielectric Resonator Modelled Using the Transmission-Line Matrix Method,” Proceedings of the Symposium on Antenna Technology and Applied Electromagnetics ANTEM-96, 1996, Montreal, Canada, pp. 709-712. 70. J. Carrie, K. Esselle, D. J. Roscoe, A. Ittipiboon, A. Sebak, L. Shafai, “A K-Band Circularly Polarized Cavity Backed Dielectric Resonator,” 1996 IEEE International Symposium on Antennas and Propagation Digest, Baltimore, MD, pp. 734-737. 71. D. J. Roscoe, M. Cuhaci, A. Ittipiboon, L. Shafai, “EHF Active Integrated Arrays Designed for Device Integration,” Proceedings of the Symposium on Antenna Technology and Applied Electromagnetics ANTEM-96, 1996, Montreal, Canada, pp. 555-558. 72. A. Petosa, R. K. Mongia, M. Cuhaci, and J. S. Wight, “Magnetically Tunable Ferrite Resonator Antenna,” Electronics Letters, 30, 13, June 1994, pp. 1021-1022.

73. A. Petosa, R. K. Mongia, A. Ittipiboon, and J. S. Wight, “Experimental Investigations on a Magnetically Tunable Ferrite Resonator Antenna,” Proceedings of the Symposium on Antenna Technology and Applied Electromagnetics ANTEM-94, 1994, Ottawa, Canada, pp. 697-700. 74. A. Petosa, R. K. Mongia, A. Ittipiboon, and J. S. Wight, “Switchable LPICP Ferrite Disk Resonator Antenna,” Electronics Letters, 31, 3 , February, 1995, pp. 163-164. 75. A. Petosa, “Ferrite and Dielectric Antennas for Personal Communications,” PhD Dissertation, Carleton University, 1995. 76. A. Petosa, R. K. Mongia, A. Ittipiboon, and J. S. Wight, “Investigation of Various Feed Structures for Linear Arrays of Dielectric Resonator Antennas,” 1995 IEEE International Symposium on Antennas and Propagation Digest, Newport Beach, CA, pp. 1982-1985. 77. M. G. Keller, M. B. Oliver, D. Roscoe, R. K. Mongia, Y . M. M. Antar, A. Ittipiboon, “Millimeter-Wave Dielectric Resonator Antenna Array,” 1995 USNC/URSI National Radio Science Meeting Abstracts, Newport Beach, CA, pp. 69. 78. R. K. Mongia, A. Ittipiboon, and M. Cuhaci, “Experimental Investigations on Microstrip-Fed Series Dielectric Resonator Antenna Arrays,” Proceedings of the Symposium on Antenna Technology and Applied Electromagnetics ANTEM-94, 1994, Ottawa, Canada, pp. 81-84. 79. A. Petosa, R. K. Mongia, A. Ittipiboon, and J. S. Wight, “Investigation on a Microstrip-Fed Series Array of Dielectric Resonator Antennas,” Electronics Letters, 31, 16, Aug. 95, pp. 1306-1307. 80. M. G. Keller, M. Fleury, E. Philippouci, A. Petosa, M. B. Oliver, “Circularly Polarized Dielectric Resonator Antenna Array,” 1996 USNCKJRSI National Radio Science Meeting Abstracts, 1996, Baltimore, MD. 81. A. Petosa, D. Roscoe, A. Ittipiboon, M. Cuhaci, “Dielectric Resonator Antennas for Mobile Satellite Applications,” Intemational Mobile Satellite Conference IMSC-97, 1997, Pasadena, CA. 82. A. Petosa, A. Ittipiboon, M. Cuhaci, R. Larose, “Bandwidth Improvement for a Microstrip-Fed Series Array of Dielectric Resonator Antennas,” Electronics Letters, 32, 7, March 96, pp. 608-609. 83. A. Petosa, D. J. Roscoe, A. Ittipiboon, and M. Cuhaci, “Antenna Research at the Communications Research Centre,” IEEE Antennas and Propagation Magazine, 38, 5, Oct. 96, pp. 714. 84. A. Petosa, R. Larose, A. Ittipiboon, and M. Cuhaci, “Microstrip-Fed Array of Multi-Segment Dielectric Resonator Antennas,” IEE Proceedings-Microwaves Antennas and Propagation, 144, 6, Dec. 1997, pp. 472 - 476.
85. G. D. Loos, Y. M. M. Antar, A. Ittipiboon, and R. K. Mongia, “Array Factor Considerations for Rectangular Dielectric Resonator Antennas,” Proceedings of the Symposium on Antenna Technology and Applied Electromagnetics ANTEM-94, 1994, Ottawa, Canada, pp. 73-79.

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IEEE Antennas and Propagation Magazine, Vol. 40, 3, June 1998 No.

86. G. D. Loos, Y. M. tangular Dielectric Re

ar, “A New Aperture-Coupled Rec-

tary College, 1994.

in Electrical Engineering from the University of Manitoba, Winnipeg, Manitoba, Canada. Since 1985, he has been with the Communications Research Centre, Ottawa, where he is currently a Senior Antenna Research Scientist. He is also an Adjunct Professor in Electrical and Computer Engineering Department, University of Manitoba. He has been involved in research and development work on novel printed antennas, dielectric antennas, and active phased arrays. His interests include applied electromagnetics, millimeterwave technology and devices, and wireless communications.

M. Cuhaci, R. Larose, “Low Profile Resonator Antennas,” IEEE InternaArray Systems and Technology, 1996, Boston, MA, pp. 1

Yahia M. M. Antar was born on November 18, 1946, in Meit Temmama, Egypt. He received the BSc (Hons) degree in 1966 from Alexandria University, Egypt, and the MSc and PhD degrees from the University of Manitoba, Winnipeg, Canada, in 1971 and 1975, respectively, all in electrical engineering. In 1966, he joined the Faculty of Engineering at Alexandria, where he was involved in teaching and research. At the University of Manitoba, he held a University Fellowship, an NRC Postgraduate, and postdoctoral Fellowships. In 1976-1977, he was with the Faculty of Engineering at the University of Regina. In June, 1977, he was awarded a Visiting Fellowship from the Government of Canada to work at the Communications Research Centre in the Department of Satellite Technology with the Space Electronics group. In May, 1979, he joined the Division of Electrical Engineering, National Research Council of Canada, Ottawa, where he worked on polarization radar applications in remote sensing of precipitation, radiowave propagation, electromagnetic scattering, and radar cross section investigations. In November, 1987, he joined the staff of the Department of Electrical and Computer Engineering at the Royal Military College of Canada, in Kingston, where he is now Professor of Electrical and Computer Engineering. He is presently the Chairman of the CNC/URSI Commission B, holds adjunct appointment at the University of Manitoba, and has a cross appointment at Queen’s University in Kingston.

market antenna-engin antennas and arrays. I Ottawa, on the develo

for computer-aided design of ed at GANDEC Corporation, anar base-station antenna arrays

Carleton University.

Apisak Ittipiboon received the BE (Hons) degree from Khonkaen University, Thailand, and the MSc and the PhD degrees

David J. Roscoe received the MSc and PhD degrees in Electrical Engineering from the University of Manitoba, Winnipeg, Manitoba, Canada in 1989 and 1993, respectively. He joined the Directorate of Antennas and Integrated Electronics at the Communications Research Centre in 1992, as a Research Scientist. He is also an Adjunct Professor with the Department of Electrical and

IEEE Antennas and Pro1 agation Magazine, Vol. 40, No. 3, June 1998

t

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Computer Engineering at the University of Manitoba, and a parttime Professor at the University of Ottawa. His primary research interests include active antennas and phased arrays.

Correction
The antenna patterns in Figures 18b and 18c, on page 19, were interchanged in the article by Brian A. Austin and Kevin P. Murray, “The Application of Characteristic-Mode Techniques to Vehicle-Mounted NVIS Antennas,” IEEE Antennas and Propagation Magazine, 40, 1, February, 1998, pp. 7-21. The Magazine regrets the error.

Changes of Address
Michel Cuhaci received the BaSC and MaSc degrees in Electrical Engineering from the University of Ottawa, Ottawa, Ontario, Canada, in 1975 and 1979, respectively. He joined the Communications Research Centre, Ottawa, in 1977, as a microwave engineer whose activities involved the design of MICs and MMICs. Since 1987, he has been the project leader for the Antennas and Component Integration group. In 1994, he initiated the study on the application of gas lattice cellular automata to EM analysis, as an alternative to conventional methods. His research activities include the design and development of phased-array antenna sub-systems, the study of novel planar radiating structures, and the development of workstation-based EM-analysis software. He is a member of the IEEE MTT and AP Societies. :F { Information regarding subscription addresses is maintained by IEEE headquarters. It is not maintained, nor can it be changed, by any member of the Magazine Staff. If you are a member of the IEEE, your subscription is sent to the address in your IEEE member record. To record a change of address, contact IEEE headquarters: Member Address Records, IEEE Headquarters, 445 Hoes Lane, Piscataway, NJ 08855-1331; Tel: (908) 981-0060 or (800) 678-4333; Fax: (908) 981-9667; E-mail: [email protected]. If you are an institutional subscriber, contact IEEE Customer Service at the above address, telephone and fax numbers; E-mail: [email protected]. Do not send requests to any member of the Magazine Staff.

1998 IEEE-APS CONFERENCE ON ANTENNAS AND PROPAGATION FOR WIRELESS COMMUNICATIONS Waltham, MA
November 2-4,1998 Plan to attend the 1998 Conference on Antennas and Propagation for Wireless Communications! As Co-chairs of the 1998 IEEE-APS Conference on Antennas and Propagation for Wireless Communications, and on behalf of the Organizing Committee, we would like to invite you to attend the conference to be held November 2-4, 1998, in Waltham, Massachusetts. It is an exciting time to be working in the field of antennas and propagation, due in no small part to the explosive growth of wireless communications. Deployment of cellular telephone equipment, PCS, and wireless local loop service is rapidly evolving worldwide. Commercial application of systems which were originally developed for defense applications, such as GPS and spread spectrum techniques, are adding new capabilities and improvements in performance to consumer applications Technical sessions will cover topics relevant to real-world problems in wireless antennas and propagation, and each session will begin with an overview presented by an expert in the field. And because this conference is small and focused, you will have the opportunity to discuss these developments with the speakers and other conference attendees. In addition, we will be hosting an exhibit hall for companies involved with wireless products, and will be conducting several short courses specifically on topics in wireless antennas and propagation. We think this will be an exciting conference, and look forward to seeing you there! David M. Pozar and Tuli Herscovici Conference Co-Chairmen For more details call the conference office at 781-890-5290, email to [email protected] or visit where you can the conference website at http://www.tiac.net/users/tuli/apwc98/advance/ review the technical program and download the registration form.

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IEEE Antennas and Propagation Magazine, Vol. 40,No. 3,June 1998

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