Diversity Dielectric Resonator Antennas for Wireless Communications

Abstract

With the continuous advancement of WiFi and mobile communication technologies, especially driven by the need to enhance throughput and expand multi-device connectivity, the demand for integrating more channels and antenna units into wireless communication systems has grown significantly. This technological trend, however, confronts a fundamental engineering paradox: strict limitations on device dimensions are imposed by high integration and industrial design considerations, resulting in competing objectives between system miniaturization and performance enhancement. To address this trade-off, multi-port diversity antennas have emerged as an effective approach. Dielectric resonator antennas (DRAs) are good candidates for diversity applications due to their low loss, high radiation efficiency, and multi-mode excitation capability. Nevertheless, conventional diversity DRAs often rely on complex feeding networks, thereby limiting their structural integration. To address this challenge, diversity DRAs from different perspectives are studied.

Chapter 1 provides a comprehensive review of existing diversity DRAs. Chapter 2 presents a tri-band polarization diversity antenna developed through a reverse design method. This method is based on three hybrid electromagnetic (HEM) modes of cylindrical DRAs (CDRAs) and enables the simultaneous excitation of the three independent resonant modes. Given three target operating frequencies, the method analytically derives the physical dimensions (radius a, height h) and dielectric constant (εr) of the CDRA. Curve-fitting empirical formulas for these three design variables are established by numerically solving the characteristic transcendental equations. The effectiveness of the proposed reverse design method is validated through the design of single- and dual-polarized tri-band DRAs operating at 1.7, 2.6, and 3.6 GHz. This methodology provides a theoretical reference for the rapid development of multi-band diversity antennas in multi-standard wireless communication scenarios.

Chapter 3 presents a quad-port pattern-diversity cross-shaped DRA. The antenna is excited by four feeding strips integrated with two printed 180° hybrid couplers. By carving a cross-shaped groove at the bottom of dielectric resonator (DR), two distinct radiation modes are simultaneously excited and controlled, significantly enhancing isolation between opposite ports. Concurrently, a central cylindrical blind hole is loaded in the DR to suppress orthogonal-port coupling and improve the peak gain of broadside patterns. This configuration generates four orthogonal radiation states, comprising two broadside beams and two bi-directional beams. Furthermore, by employing external power dividers, the main beams can be tilted to form an additional set of diversity patterns, thereby expanding the pattern coverage. This design is a promising candidate for intelligent Wi-Fi systems that can support different scenarios.

Chapter 4 extends the cross-shaped DRA from Chapter 3 to realize a polarization-diversity design supporting both linear and circular polarization (CP). The cylindrical hole is evolved into a cross-shaped aperture. By optimizing its dimensions, a stable broadside radiation mode is excited via a single feeding strip, effectively suppressing the pattern deflection induced by asymmetric feeding. The proposed DRA supports independent excitation for four linear polarization states, or can be integrated with 90° hybrid couplers to achieve polarization-diversity CP operation, demonstrating functional versatility.

In summary, three compact diversity DRA designs are studied to meet the requirements for multi-frequency polarization diversity, pattern diversity, and CP diversity antennas, respectively. These designs provide highly integrated and multifunctional antenna solutions for advanced wireless communication applications.

Date of Award	12 Aug 2026
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Kwok Wa LEUNG (Supervisor)