論文摘要 : 介質EBG有非常多的好處,它可以配置成反射面,也可以配置為覆蓋層,這兩種配置皆可以提升天線的輻射特性,並且和金屬的EBG相比,可以有更低的歐姆損耗。根據EBG的結構配置可以分為三大類,即一維的柱狀排列,二維的平面式排列,及三維的立體狀結構。三維的立體狀結構有更多的好處以及更多的設計自由度,然而因為實作上的困難,使得其在微波上的研究及應用受到侷限。受惠於積層製造技術以及奈米科技的進步,複雜的3D陶瓷或介質結構已能被製作出來。考量EBG整體結構的整體尺寸以及對製程精度的要求,我們認為28GHz的毫米波頻段是個適合嘗試採用積層製造技術來製備天線元件的候選頻段。 在此論文中,我們將先設計一個工作在28GHz的典型平面式woodpile EBG。EBG的各項設計參數將被仔細分析並且探討它們對天線性能上的影響。之後,此論文提出一個弧形的EBG設計。我們發現弧形的EBG可以改善天線的輻射場型,提供更好的指向性。散射參數及輻射場型等天線參數皆有提供以證明在偶極天線上,弧形狀的設計可以比平面式的設計提供更佳的性能。
Abstract : Dielectric electromagnetic band-gap (EBG) has many advantages. It can be configured as a reflector, or be configured as a superstrate. Both of this two configurations can improve antenna radiation preference with lower conduction loss as compared to metallic EBG. In general, EBG can be categorized into three groups according to their geometric configuration, which are one-dimensional rods, two-dimensional planar surfaces, and three-dimensional volumetric structures. The 3D structure has more advantages and design flexibility, however, due to the difficulties in prototyping, studies and applications in microwave field is limited. Thanks to the progress in additive manufacturing and nano-technology, dielectric or ceramic complex 3D structure is able to be fabricated. Considered the overall size of an EBG structure and the accuracy required of the fabrication process, 28GHz mmWave band is a good candidate, which has the feasibility of applying additive manufacturing in the production of antenna parts. In this thesis, a classic planar woodpile EBG working at 28GHz will be designed. Design parameters will be carefully analyzed and studied their effects on antenna performances. After that, a curved dielectric EBG with be proposed. It was found that a curved EBG can improve radiation pattern, providing higher directivity of the antenna. Antenna parameters such as scattering parameters and radiation patterns are provided to validate that the curved design provides better performance with a dipole antenna than the planar one.
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