Novel Coplanar-Waveguide Coupled Structures with Finite-Extent Backed Conductor

• Main Authors: Chun-Lin Liao, 廖俊霖
• Other Authors: Chun Hsiung Chen
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/74430710294227868231

博士 === 國立臺灣大學 === 電機工程學研究所 === 90 === Novel edge-coupled coplanar-waveguide (CPW) structures with floating backed conductor are analyzed. To this end, the effective dielectric constants and characteristic impedances of several CPW coupled structures are discussed. These coupled structures include the CPW edge-coupled structures with and without central ground plane, those with and without infinite backed conductor, and those with finite-extent backed conductor. Two numerical methods are used to analyze the coupled structures, which include the quasistatic technique based on the conformal mapping method, and the fullwave spectral-domain approach based on proper basis functions. Specifically, the coupling coefficients of the new coupled structures can be controlled by adjusting the width of the finite-extent backed conductor. The electric current and field distributions of the novel coupled structures for different modes are presented and compared. For design purpose, a theoretical transmission-line model for the directional coupler is established, which is based on the characteristic parameters of the related coupled CPW structures. In this study, two conductor-backed edge-coupled CPW directional couplers with moderate (-6dB) and tight (-3dB) coupling coefficients are designed and implemented based on the theoretical transmission-line model. The theoretical results are compared with the measured ones, and the agreement among them confirms the usefulness of the coupler design model as well as the fullwave approach for the related coupled CPW structures.