A novel coupling scheme to a rectangular dielectric resonator antenna is proposed and investigated. In particular, coupling to the resonator is achieved through a narrow slot at the end of a coplanar waveguide (CPW). The objectives of this design are to maximize the coupling, match the dielectric resonator to the CPW feed line, achieve resonance at the desired frequency, obtain linear polarization with low cross polarization components, and minimize back radiation without using a back conductor. An approximate and quick design approach is given followed by more accurate design and analysis using commercial software. The antenna was fabricated and tested. Measurements match well with simulation results.

Coplanar-waveguide-fed slot-coupled rectangular dielectric resonator antenna

A dualband dielectric resonator antenna (DRA) is designed by splitting a rectilinear dielectric resonator (DR) and carving notches off the DR. It is observed that notches engraved at different positions affect different modes. Removal of dielectric material from where the electric field is strong incurs a significant increase in resonant frequency. The abrupt change of normal electric field across the discontinuities reduces the -factor and increases the impedance bandwidth. Both the and modes incur broadside radiation patterns on the -plane. The proposed DRA can cover both the worldwide interoperability for microwave access (WiMAX, 3.4-3.7-GHz) and the wireless local area network (WLAN, 5.15-5.35-GHz) bands.

Dualband Split Dielectric Resonator Antenna

A broadband dielectric resonator (DR) antenna is designed by merging its three resonant bands. An asymmetrical moat carved off the DR is designed to perturb the electric field distribution within the DR so that the Q factor of the DR is reduced, and the radiation pattern on the E-plane can be modified to increase the gain in the broadside direction. The mode mixing effect on the radiation patterns is also studied. A wide impedance bandwidth of 33%(4.89-6.86 GHz) is obtained with broadside radiation pattern of vertical polarization on the horizontal plane. This DR antenna can be used for WLAN 802.11a (5.15-5.85 GHz) applications.

Bandwidth Broadening of Dielectric Resonator Antenna by Merging Adjacent Bands

A wideband rectangular dielectric resonator (DR) with a horizontal tunnel is proposed. The bandwidth of the TEy 111 mode is increased by using the tunnel to reduce the Q-factor of the DR. As the tunnel height is increased, the electric field distribution of the TEy 112 mode is significantly modified such that its electric field distribution near the top surface of DR is similar to that of the TEy 111 mode, rendering a broadside radiation pattern. The band of the modified TEy 112 mode is merged with that of the TEy 111 mode to achieve a wide bandwidth of 20% (4.765.86 GHz) with broadside radiation pattern of vertical polarization on the xy-plane. The proposed DR antenna can be used in WLAN 802.11a applications.

http://www.mse.ntu.edu.tw/~frontier/2009,%20Antennas%20and%20Wireless%20Propagation%20Letters,%20IEEE,%207,%20275-278..pdf

Wideband Dielectric Resonator Antenna With a Tunnel

Two segmented dielectric-resonator antennas have been investigated. A weighted average model is used to predict the resonant frequency. A simple method is then introduced to optimize the lower segment of the antenna. Finally, a fast and efficient design algorithm is presented. Three examples are used to implement the methods and the algorithm in three different frequency bands. Impedance bandwidths of up to 30% are achieved with the optimum design. © 2005 Wiley Periodicals, Inc. Microwave Opt Technol Lett 45: 533–537, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20871

Investigations on Two-Segment Dielectric Resonator Antennas

Based on the concept of effective dimensions, a modification to the conventional waveguide model (CWGM), usually used to predict the resonant frequency of rectangular DRA, is introduced. Compared with the experimental results, it is found that this newly introduced MWGM yields more accurate results for the resonant frequency than the CWGM. Accuracy of the results is also checked by comparison with numerically calculated values using a TLM-based commercial software. It is also found that the MWGM not only yields accurate values, but also results in considerable computation time savings. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 19: 158–160, 1998.

Modified waveguide model (MWGM) for rectangular dielectric resonator antenna (DRA)

The uniaxial chiral medium, which is a modification of well-studied reciprocal chiral material, can be created by embedding microscopic metal helices in an isotropic host medium in such a way that the axes of all helices are oriented parallel to a fixed direction but distributed in random locations. Based on the concept of characteristic waves and the method of angular spectral expansion, cylindrical vector wave functions are rigorously developed to represent the electromagnetic fields in a source-free uniaxial chiral medium. Analysis reveals that the solutions of the source-free vector wave equation for uniaxial chiral medium, which are composed of two transverse waves and a longitudinal wave, can be represented in sum-integral forms of the cylindrical vector wave functions. The addition theorem of the vector wave functions for a uniaxial chiral medium can be directly obtained from its counterpart for the isotropic medium. To widen the application scope of the present cylindrical vector wave functions in a uniaxial chiral medium, a generalized mode-matching method is also proposed to study the two-dimensional electromagnetic scattering of a cylinder with an arbitrary cross section, and a conducting circular cylinder with an inhomogeneous coating thickness. To check the convergence of the present cylindrical vector wave functions for the multiple-body problem, electromagnetic scattering of two circular cylinders of uniaxial chiral media is also investigated. Excellent convergence properties of the cylindrical vector wave functions in these application examples are numerically verified, which establishes the reliability and applicability of the present cylindrical vector wave functions.

Cylindrical vector wave functions and applications in a source-free uniaxial chiral medium

Electromagnetic scattering by a uniaxial chiral cylinder with arbitrary cross section: Generalized mode‐matching method

Recent Advances of Beta Zeolite in the Volatile Organic Compounds(VOCs) Elimination by the Catalytic Oxidations

Based on the eigenfunction expansion of electromagnetic waves in a reciprocal uniaxial bianisotropic medium, an extended mode-matching method is proposed to study the scattering of an infinitely long reciprocal uniaxial bianisotropic cylinder with arbitrary cross section. Excellent convergence of the echo width is numerically verified, which establishes the reliability and applicability of the present extended mode-matching method for the two-dimensional single-body problem in which the reciprocal uniaxial bianisotropic medium has a curved surface.

Dajun Cheng

Papers

Modified waveguide model (MWGM) for rectangular dielectric resonator antenna (DRA)

Cylindrical vector wave functions and applications in a source-free uniaxial chiral medium

Electromagnetic scattering by a uniaxial chiral cylinder with arbitrary cross section: Generalized mode‐matching method

Recent Advances of Beta Zeolite in the Volatile Organic Compounds(VOCs) Elimination by the Catalytic Oxidations

Electromagnetic scattering by a reciprocal uniaxial bianisotropic cylinder with arbitrary cross section: extended mode-matching method