西安电子科技大学专业学位硕士学位论文模版(2014年修订版)(11)

西安电子科技大学专业学位硕士学位论文最新模版(2014年修订版)。

ABSTRACT

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

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