| In recent years, dielectric resonator antennas (DRA) and broadband printed slot antennas have been widely studied owing to their good performances. Due to their several advantages such as wide bandwidth, high efficiency and ease of excitation, DRAs have been widely used in millimeter wave regions. Broadband printed slot antennas are widely used in modern wireless communications due to their advantages of low profile, simple fabrication process and ease of integration with circuits. This dissertation is mainly concerned with the design and implementation of various DRAs and broadband printed slot antennas. The author's major contributions are outlined as follows:1. Two broadband printed slot antennas have been studied. Firstly, according to the requirements of wireless communication systems, a coplanar waveguide (CPW) fed broadband printed slot antenna covering IMT-2000, WiMAX and WLAN bands is designed. The resonant frequencies of the antenna are adjusted by changing the structures of the slot and the coplanar waveguide. An impedance transformer is introduced to realize broadband impedance match. Secondly, a microstrip fed printed elliptical wide-slot antenna is proposed for ultra-wideband applications. The ultra-wideband impedance match is achieved by adjusting the axial ratio of the elliptical slot and the elliptical annular patch.2. Two broadband DRAs have been studied. Firstly, a slot-fed broadband cylindrical DRA is designed by using the following three methods: introducing air gap to reduce the internal Q-factor of the DRA, choosing the appropriate thickness of the air gap to make the DRA working at several modes with similar radiation patterns, and adding hexagon stub at the end of the feed line for the DRA impedance match. Secondly, a CPW-fed ultra-wideband DRA is proposed by using the combination of crescent-shaped printed monopole and DRA. The experimental results show that these two antennas have good broadband performance.3. A broadband circularly-polarized (CP) DRA and a dual linear-polarized DRA with high isolation have been studied. Firstly, a broadband circularly polarized cylindrical DRA excited by annular slot coupling is proposed. The broadband CP radiation has been achieved by using two CP radiators, DRA and annular slot. In addition, an impedance transformer is introduced to improve the impedance bandwidth. Secondly, a dual linearly polarized rectangular dielectric resonator antenna with high isolation operating at around 5.2 GHz for WLAN applications has been presented. The high isolation is achieved by using two hybrid feeding mechanism: one port having an H-shaped aperture coupled feed and the other with probe feed. Two out-of-phase probe feed is used to avoid the asymmetric radiation pattern caused by single probe feed.4. A compact DRA has been studied. Several techniques used for reducing the size of a DRA are discussed. By using the shorting posts, a modified compact DRA is designed. Comparing with several existing antennas, the radiation patterns deformation could be avoided and the cross polarization levels are reduced, by using shorting posts instead of the shorting plate.5. A high-gain DRA linear array has been studied. Based on the analysis results of the high-order modes of the rectangular DRA, a high-gain DRA element is selected to design an 8-element high-gain DRA linear array. The effect of spacing between adjacent elements on the gain of the array is analyzed. In addition, it is found that the gain of the proposed DRA linear array is higher than the microstrip patch linear array with the same aperture area. Finally, an 8-element DRA linear array prototype is constructed to validate the feasibility and efficiency of the design. |
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