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S.-L. Lai

Bio: S.-L. Lai is an academic researcher from South China University of Technology. The author has contributed to research in topics: Band-pass filter & Waveguide filter. The author has an hindex of 2, co-authored 3 publications receiving 56 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the fundamental broadside TM110 mode of an aperture-coupled circular dielectric resonator antenna was studied and the return loss, radiation characteristics, antenna gain and beamwidth of the configuration were measured and discussed.
Abstract: The fundamental broadside TM110 mode of an aperture-coupled circular dielectric resonator antenna is studied. By using high-dielectric-constant material, the DR antenna can be made low-profile with a relatively low resonant frequency. The return loss, radiation characteristics, antenna gain and beamwidth of the configuration are measured and discussed.

49 citations

Journal ArticleDOI
TL;DR: In this article, the microwave dielectric properties of Ba(Zn1/3Ta2/3)O3 and Ba(Cd 1/3Nb 2/3 )O3 were investigated.
Abstract: Microwave dielectric properties of Ba(Zn1/3Ta2/3)O3–Ba(Cd1/3Nb2/3)O3 ceramics are presented. Sintering of Ba(Zn1/3Ta2/3)O3 was accelerated by the addition of Ba(Cd1/3Nb2/3)O3, and the microwave Q value was also improved. As ZnO volatilises from the sample, the crystallographic distortion was compensated, and the improved microwave loss quality, Q, was explained.

6 citations

Journal ArticleDOI
TL;DR: In this paper, a triple-mode microwave filter using only TM mode degeneracies is presented, where the TM degeneracy is applied to the design of satellite communications filters and multiplexers.
Abstract: Triple-mode degeneracy in cylindrical cavities has been successfully applied to the design of satellite communications filters and multiplexers. Previous approaches have employed either dual-TE/single-TM or dual-TM/single-TE mode combinations. A novel realisation of a triple-mode microwave filter using only TM mode degeneracies is presented.

2 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the authors present a historical review of the research carried out on dielectric resonator antennas (DRAs) over the last three decades and highlight major research activities in each decade.
Abstract: This article presents a historical review of the research carried out on dielectric resonator antennas (DRAs) over the last three decades. Major research activities in each decade are highlighted. The current state of the art of dielectric-resonator-antenna technology is then reviewed. The achievable performance of dielectric resonator antennas designed for compactness, wide impedance bandwidth, low profiles, circular polarization, or high gain are illustrated. The latest developments in dielectric-resonator-antenna arrays and fabrication techniques are also examined.

494 citations

Journal ArticleDOI
Wolfram Wersing1
TL;DR: In this paper, the properties of microwave ceramics, particularly the property-structure relationship, have been investigated and new materials with higher permittivity, better temperature stability and considerably lower sintering temperature have been developed.
Abstract: High-permittivity ceramics make it possible to noticeably miniaturize passive microwave devices. These ceramics must fulfil the requirements of high permittivity, very low dielectric losses and an extremely low temperature dependence of permittivity to yield temperature-stable resonators. Recent progress has been made in understanding the physics of microwave ceramics, particularly the property-structure relationship, in developing new materials with higher permittivity, better temperature stability and considerably lower sintering temperature, and in making co-fired multilayer devices possible, as well as in developing new microwave devices such as oscillators, antennas and band-pass filters.

427 citations

Journal ArticleDOI
TL;DR: In this article, several electrically small resonant antennas employing the composite right/left-handed transmission line (CRLH-TL) are presented for integration with portable RF modules.
Abstract: Several electrically small resonant antennas employing the composite right/left-handed transmission line (CRLH-TL) are presented for integration with portable RF modules. The proposed antenna designs are based on the unique property of anti-parallel phase and group velocity of the CRLH-TL at its fundamental mode. In this mode, the propagation constant increases as the frequency decreases, therefore, a small guided wavelength can be obtained at a lower frequency to provide the small lambdag/2 resonant length used to realize a compact antenna design. Furthermore, the physical size and the operational frequency of the antenna depend on the unit cell size and the equivalent transmission line model parameters of the CRLH-TL, including series inductance, series capacitance, shunt inductance and shunt capacitance. Optimization of these parameters as well as miniaturization techniques of the physical size of unit cell is investigated. A four unit-cell resonant antenna is designed and tested at 1.06 GHz. The length, width and height of the proposed antenna are 1/19lambda0, 1/23lambda0 and 1/83lambda0, respectively. In addition, a compact antenna using a 2-D three by three mushroom like unit cell arrangement is developed at 1.17 GHz, showing that an increased gain of 0.6 dB and higher radiation efficiency can be achieved over the first prototype antenna. The same design is applied in the development of a circularly polarized antenna operating at 2.46 GHz. A 116deg beamwidth with axial ratio better than 3 dB is observed. The physical size of the proposed mushroom type small antenna and the circularly polarized antenna is 1/14lambda0 by 1/14lambda0 by 1/39lambda0 and 1/10lambda0 by 1/10lambda 0 by 1/36lambda0, respectively

341 citations

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a circular polarization design of microstrip antennas and dielectric resonator (DR) antennas through a cross slot of unequal slot lengths in the ground plane of a microstrip line, which results in the excitation of two near-degenerate orthogonal modes of near equal amplitudes and 90/spl deg/phase difference.
Abstract: Circular polarization (CP) design of microstrip antennas and dielectric resonator (DR) antennas through a cross slot of unequal slot lengths in the ground plane of a microstrip line is demonstrated. The proposed CP design is achieved by choosing a suitable size of the coupling cross slot, which results in the excitation of two near-degenerate orthogonal modes of near-equal amplitudes and 90/spl deg/ phase difference. This CP design can be applied to both configurations of microstrip antennas and DR antennas and has the advantages of easy fine-tuning and less sensitivity to the manufacturing tolerances, as compared to their respective conventional single-feed CP designs. For the proposed design applied to a low-profile circular disk DR antenna of very high permittivity studied here, a large CP bandwidth, determined from 3-dB axial ratio, as high as 3.91% is also obtained. Details of the proposed antenna designs are described, and experimental results of the CP performance are presented and discussed.

243 citations

Journal ArticleDOI
TL;DR: In this article, a wideband, low profile and high gain dielectric resonator antenna with two different permittivities is proposed. But the antenna is not suitable for wideband applications.
Abstract: A wideband, low profile and high gain dielectric resonator antenna is investigated in this letter. The antenna consists of two dielectric layers with different permittivities and it is centrally fed by a rectangular slot. By placing the dielectric layer of low permittivity (2.2) below that of high permittivity (15), the antenna with low profile of $0.1{\lambda _0}$ can obtain a 10-dB impedance bandwidth of $\sim 40\% $ and an average gain of $\sim 9~\hbox{dBi}$ .

118 citations