Rigorous analysis of the hemispherical dielectric resonator antenna with a parasitic patch

Abstract

This dissertation presents a parasitic patch technique employed to the hemispherical dielectric resonator antenna (DM). Because of the simple interface between the hemispherical dielectric resonator (DR) and air, an exact analysis can be formulated. Various Green's functions are derived rigorously by using the mode-matching method. The slot and patch currents are solved using the Method of Moments (MoM). The parasitic patch can be used to change the characteristics of the DRA. Because of the parasitic patch, an additional resonant mode is generated which widens the bandwidth. By changing the slot length, the impedance matching can be achieved. Exciting circularly polarized (CP) DRA is another function of using the parasitic patch. By choosing proper patch dimensions, two nearly degenerate orthogonal modes can be excited, leading to a CP operation. Two different excitation methods are studied. The first one is the conducting conformal strip excitation, implemented by cutting a strip from an adhesive conducting tape. The second excitation method is the aperture-coupled DRA fed by a microstripline, which improves the asymmetrical problem found in the previous one. Measurements were carried out to verify the results. The complex resonant frequencies of a slot-loaded DRA and a parasitic-patch-loaded DRA are discussed. The real resonant frequencies and Q-factors can be retrieved from the complex resonant frequencies, which facilitate engineers to design antennas with DRA. Using appropriate parasitic-patch dimensions, a CP DRA was excited, giving a 3-dB axial ratio bandwidth of ~3%. For the wideband case, a DRA of ~17% bandwidth was fabricated. To minimize the cross polarization, the aperture-coupled DRA fed by a microstripline was used. The co-polarized fields are at least 20dB stronger than the cross-polarized fields in boresight direction.

Date of Award	2 Oct 2003
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Kwok Wa LEUNG (Supervisor)