IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 8, 2009 173
A Compact Dual-Band Dielectric Resonator
Antenna Using a Parasitic Slot
Hua-Ming Chen, Senior Member, IEEE, Yang-Kai Wang, Yi-Fang Lin, Shih-Chieh Lin, and Shan-Cheng Pan
Abstract—A compact dual-band dielectric resonator antenna
(DRA) using a parasitic c-slot fed by a microstrip line is proposed. In this configuration, the DR performs the functions of an effective radiator and the feeding structure of the parasitic c-slot in the ground plane. By optimizing the proposed structure parameters, the structure resonates at two different frequencies. One is from the DRA with the broadside patterns and the other from the c-slot with the dipole-like patterns. In order to determine the performance of varying design parameters on bandwidth and resonance frequency, the parametric study is carried out using simulation software High-Frequency Structure Simulator and experimental results. The measured and simulated results show excellent agreement.
Index Terms—Ceramic dielectric material, dielectric resonator
antenna (DRA), dual band, microstrip feedline.
I. INTRODUCTION
T
HE DIELECTRIC resonator antenna (DRA) [1], [2] has been of interest due to their low loss, high permittivity, light weight, and ease of excitation. In addition, wide band-width, low dissipation loss at high frequency, and high radia-tion efficiency due to the absence of conductors and surface-wave losses are inherent advantages of DRAs. In the past few years, theoretic and experimental investigations have been re-ported by many researchers on DRAs of cylindrical, rectangular, and hemispherical shapes [1]–[15]. The use of dielectric res-onators in feeding circuits requires accurate knowledge of the coupling between the resonator and circuits. In order to match the DR to the feedline and to excite the desired mode in the res-onator, the most common method of feeding techniques is the aperture-coupled arrangement [3]–[5]. Recently, hybrid dielec-tric resonator antennas have attracted extensive attention due to their dual-band and wideband operation without increasing an-tenna volume. The hybrid structure can be considered as the combination of a DRA and another radiating resonator of the resonant feeding structure. These two radiating resonators are tightly stacked together and resonate at different frequencies.Manuscript received May 06, 2008. First published June 10, 2008; current version published April 22, 2009. This work was supported by the National Science Council of Taiwan under Contract NSC 95-2221-E-151-017.
H.-M. Chen, Y.-F. Lin, and S.-C. Lin are with the Institute of Photonics and Communications, National Kaohsiung University of Applied Sciences, Kaoh-siung 807, Taiwan (e-mail: hmchen@cc.kuas.edu.tw; linyf@cc.kuas.edu.tw).
Y.-K. Wang is with the Department of Electrical Engineering, National Kaoh-siung University of Applied Sciences, KaohKaoh-siung 807, Taiwan.
S.-C. Pan is with the Department of Computer and Communication, Sue-Te University, Yen Chau, Kaohsiung 824, Taiwan.
Color versions of one or more of the figures in this letter are available online at http://ieeexplore.ieee.org.
Digital Object Identifier 10.1109/LAWP.2008.2001119
Fig. 1. Top view and side view of the dual-frequency DRA.
By arranging for the radiating resonators’ position, a compact dual-band [6]–[9], wideband [10]–[13], or frequency-tunable [14], [15] hybrid DRA can be designed. However, the reso-nant feeding structure adopted in these reported designs, such as microstrip-fed aperture-coupled, loop slot, or CPW-fed slot arrangement offers more flexibility and is directly compatible with different mounting surfaces.
In this letter, in order to avoid via holes and for ease of fab-rication, the microstrip line feed to DRA is adopted as shown in Fig. 1. The DRA operates in its fundamental mode, and it is used as the parasitic c-slot feeding structure at the same time. It will be fond that by varying the size of the parasitic c-slot, the operating frequency of the slot mode can be adjusted easily. This design has the advantage of simple structure, com-pact size, and can achieve dual band with different radiating pat-terns. This proposed DRA is suitable to be mounted above the system circuit board of the mobile-communication device, and is very suitable for applications in mobile-communication sys-tems.
II. ANTENNACONFIGURATION
The proposed dual-band DRA structure is shown in Fig. 1. It consists of a circular disk DR and a center-fed microstrip line which is printed on an FR4 substrate of thickness mm and relative permittivity . The ground plane is printed on the FR4 substrate with a dimension of mm . The DRA has a diameter of mm, a height of
mm, and a relative permittivity of . Its res-onance mode can be excited for the aspect ratio less than unity [2]. The center point of DR is placed above the center line of the ground plane with an offset distance which is used to adjust the coupling energy between the microstrip-fed line
176 IEEE ANTENNAS AND WIRELESS PROPAGATION LETTERS, VOL. 8, 2009
Fig. 10. Measured and simulated x-z plane and y-z plane radiation patterns at 2.4 GHz.
Fig. 11. Measured and simulated x-z plane and y-z plane radiation patterns at 5.6 GHz.
because the dielectric and conductor losses are not considered in the simulation. The patterns in the yz-plane are near omni-directional when compared to the conventional dipole antenna because of the asymmetric DR loading on the c-slot. In addition, the proposed antenna radiates a maximum in the broadside di-rection in the xz- and yz-planes at 5.6 GHz, which corresponds to the far-field radiation from the resonant mode of the DRA and as shown in Fig. 11. It should be mentioned that the ra-diating patterns in the two planes along the back side have large back radiation, which is because of the effect of bidirectional radiations for the slot antenna. Fig. 12 presents the measured antenna gain in the broadside direction throughout the two frequency bands. The measured gain was obtained using the gain transfer method where a standard gain horn antenna was used as a reference. The measured peak gain is about 3 dBi for the 2.36–2.5 GHz band, and in the 5.4–5.8 GHz band, the antenna peak gain is about 3.5 dBi.
V. CONCLUSION
A miniature dual-band dielectric resonator antenna with a parasitic c-slot fed by a microstrip line has been proposed and tested. A parametric study is carried out to investigate the an-tenna design parameters. The prototype has been designed and fabricated and found to have a bandwidth and antenna peak gain of 3.3%, 4.3 dBi, and 5.7%, 3.8 dBi at the resonant frequencies of 2450 and 5640 MHz, respectively. The proposed antenna is
Fig. 12. Measured antenna gain of the hybrid antenna in the broadside( = 0 ).
small, and has an effective feeding structure and adequate oper-ational bandwidth, such that it is suitable for use in communi-cation system applicommuni-cations.
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