Dielectric antennas for circular polarization, wide- and dual-band operation, and differential excitation

Abstract

This dissertation is dedicated to the design and analysis of the dielectric resonator antenna (DRA) and dielectric-loaded slot antenna. The numerical finite-difference time-domain (FDTD) method and the commercial software package Ansoft HFSS were used in this dissertation. The first part of the dissertation concentrates on the circularly polarized (CP) and wideband DRAs, as well as the novel DRA feeding technique. In the CP DRAs, the strip-fed and aperture-coupled CP rectangular DRAs with parasitic patches are studied. It is followed by the cavity-backed CP cylindrical DRA excited by an asymmetrical U slot. A cross-slot-coupled CP hemi-ellipsoidal DRA (HEDRA) is also proposed. It is found that it is easier to match the CP HEDRA than for its hemispherical counterpart. A wideband strip-fed rectangular DRA is analyzed rigorously. Use is made of simultaneous excitations of the fundamental TE111 and higher-order TE113 modes to obtain a wide impedance bandwidth of ~ 43 %. By using the dielectric waveguide model (DWM), the resonance frequencies of the two modes can be determined accurately. Based on this DRA configuration, a quadrature-fed rectangular DRA for wideband CP applications is proposed. The DRA can achieve a very wide axial ratio (AR) bandwidth of ~ 35 %. Apart from the CP and wideband DRAs, a differentially fed rectangular DRA is also studied for the first time. It is found that the fundamental TE111 mode of the rectangular DRA can be excited. The effects of the magnitude and phase imbalances on the DRA impedance and radiation pattern are investigated. The second part of this dissertation presents a compact dielectric-loaded dual-slot antenna for dualband applications. The slots are cut onto an L-probe-fed hollow rectangular conducting cavity, which is covered by a protective dielectric layer. The two slots give two resonance modes that lead to a dualband operation. It is favorable that the frequencies of the two resonance modes can be designed independently, which greatly facilitates the dualband design. To demonstrate the idea, a dualband antenna for 2.4/5.2-GHz IEEE802.11a/b WLAN applications is designed and tested.

Date of Award	2 Oct 2007
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Kwok Wa LEUNG (Supervisor)