新型非對稱式共平面波導結構零階共振天線之頻寬增加與效率提升

Abstract

本論文提出新型波導結構應用在基於複合式左右手材料(composite right/left-handed transmission line, CRLH)的零階共振天線(Zeroth-Order Resonant Antenna, ZOR antenna)。因為零階共振天線的特性使的天線的尺寸可以被大幅的縮小，以至於最近幾年零階共振天線的研究引起相當多的關注。然而極窄頻是為零階共振天線缺點，使得此類天線欲應用於無線通訊系統上須先克服頻寬被限制的問題。本論文提出了製作於單層板上的非對稱式共平面波導結構(Asymmetric Coplanar waveguide, ACPW) 使得零階共振天線的頻寬得以大幅增加、提升了天線的效率、有好的天線增益並且保持零階共振體積尺寸小的優點。非對稱式結構維持了傳統共平面波導(CPW)設計自由度高的特性，並且克服了共平面波導的設計限制。 本論文前半部建立必要的複合式左右手材料的特性，並且分析零階共振的物理機制與一般零階共振天線的特性，並由微帶線與共平面波導的例子發現：由任意CRLH-TL 所製作的ZOR antenna 存在著頻寬極窄的缺點，並不是所有的CRLH-TL都能適合的應用在ZOR antenna上。在本論文後半部提出本論文重點：基於非對稱式共平面波導的零階共振天線( ACPW ZOR antenna )。本論文設計出了ACPW的導波結構，並且設計出建立在其上的電路單元，並實現出寬頻高效能的零階共振天現。在本研究所提出的ACPW ZOR antenna不論在尺寸、頻寬、天線效率、天線增益的表現上都遠比一般零階共振天線突出，且和近期國際期刊其它零階共振天線相比皆有所突破與斬獲。

In this paper, we propose the new type of zeroth-ordered antenna (ZOR antenna) based on composite right/left-handed transmission line (CRLH-TL). The feature of ZOR based on periodic structure is employed to reduce the antenna size. Therefore, the researches of ZOR antenna have gathered great importance in recent years. However, these antennas are suffered from narrow bandwidth generally such that it is hard to apply to wireless communication systems. This new type of CRLH-TL is based on asymmetric coplanar-waveguide (ACPW). ACPW is proposed to realize a bandwidth-extended antenna. The ACPW structure not only provides the design freedom but also overcome the design constraint of the traditional CPW. The ACPW ZOR antenna is verified by both full-wave simulations and experiments. As an advantage of the proposed method, the size of antenna is reduced and has good radiation efficiency, extended fractional bandwidth and good peak gain with omni-direction.