Abstract
Dielectric resonator antenna (DRA) has been widely studied since its introduction in 1983. Conventional DRAs typically employ a ceramic block with a single dielectric constant to achieve desired radiation characteristics. To enhance design flexibility, this thesis proposes using dielectric inserts for DRA designs, with their dielectric constant higher than that of their surrounding dielectric. Based on this idea, three distinct DRA designs with integrated filtering or reconfigurable functionalities are investigated.First, a single-band filtering substrate-integrated DRA (SIDRA) is investigated by stacking up three substrates. The top, middle, and bottom substrates are associated with the DR, substrate-integrated waveguide (SIW), and slot-coupled feedline, respectively. For the top substrate, the DR is fabricated by removing part of the copper cladding to obtain a radiation aperture. The DR is centrally loaded by dielectric inserts to reduce its size. These inserts, named as dielectric vias, are realized by filling holes in the substrate with high-dielectric-constant powder. They can increase the effective dielectric constant of the substrate and thus lower the resonant frequency of the DRA. In the middle substrate, two orthogonal slots and two metallic posts are used to introduce two transmission zeros for a filtering response. In the bottom substrate, a U-slot is etched in the feedline to enhance out-of-band suppression. Building on the single-band design, a dual-band filtering SIDRA is proposed for the first time, with its upper band generated by two high-order SIW modes.
The second part of this thesis investigates a frequency-reconfigurable DRA with movable dielectric inserts. Four cylindrical dielectric posts are inserted into a dielectric block to change the resonant frequency. A piezoelectric bending actuator, driven by two DC bias voltages, is deployed to move the dielectric posts vertically. This mechanical tuning approach avoids routing RF signals through the actuator, achieving a total antenna efficiency exceeding 90% across the frequency tuning range. It significantly outperforms conventional tuning methods, which rely on lossy varactors or PIN diodes.
Finally, this thesis investigates a polarization-reconfigurable DRA with movable dielectric posts (inserts). It can switch between three polarization modes: one linear-polarization (LP) mode and two circular-polarization (CP) modes. The DRA comprises a square dielectric block with four chamfered arms to obtain a wide axial ratio bandwidth. To generate a CP mode, two sets of dielectric posts are used to perturb the E-field distribution inside the DRA. Their vertical positions are adjusted by two sets of DC-voltage-controlled piezoelectric bending actuators, enabling dynamic polarization switching.
In summary, this thesis demonstrates the versatility and effectiveness of dielectric inserts in advanced DRA designs, offering promising solutions for future wireless systems.
| Date of Award | 11 Sept 2025 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Kwok Wa LEUNG (Supervisor) |