Dual-Band Stub-Tapped Coupled-Line Couplers

• Main Authors: Ting Yi Lin, 林庭毅
• Other Authors: K. S. Chin
• Format: Others
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/16417053098606579416

碩士 === 長庚大學 === 電子工程學系 === 99 === The purpose of this thesis is to develop the circuit structures and synthesis methods of the dual-band stub-tapped coupled-line couplers. In modern communication systems, microstrip couplers are useful because of they provide output signals with desired power split ratios and with 90 or 180 phase difference. Coupled-line couplers are favored and are often adopted in communication systems for their planar, simplicity, and ease of manufacture, which enhances their practicality. Since the conventional coupled-line couplers require their electrical lengths corresponding specific wavelengths, they only can be used for single band applications. There is an increasing demand for dual-band wireless communication systems that enable user access to various services. For this reason, how to enable single coupled-line coupler operated in dual bands is a popular research topic recently. Accordingly, this work proposes the novel circuit structures of stub-tapped coupled lines instead of using the conventional /4 coupled lines for dual-band operation. The T-shaped coupled lines have excellent dual-band performance for realization of couplers. Moreover, the dual-band couplers with stepped-impedance-stub coupled lines can have design flexibility because of their increased non-uniform impedances. The synthesis method is developed and found that it has several degrees of freedom which can be exploited to realize the arbitrary frequency ratio, miniaturize circuit size and replace impractical impedances with more realizable ones. In addition to the formulation and simulation, this work also fabricates several dual-band couplers with T-shaped coupled lines and stepped-impedance-stub coupled lines to demonstrate the capability of the proposed circuit structures. The measured results validate the superior performances are achieved.