Leakage Phenomena and Multimode Effects of Planar and Coplanar Transmission Lines

• Main Authors: Ching-Cheng Tien, 田慶誠
• Other Authors: Ching-Kuang Tzuang
• Format: Others
• Language: en_US
• Published: 1993
• Online Access: http://ndltd.ncl.edu.tw/handle/77578510555177789454

博士 === 國立交通大學 === 電子研究所 === 81 === The open nature of the planar and coplanar transmission line can cause leakage that results in cross-talk between neighboring elements and loss of power. In such leaky waveguides, the effects of practical structural dimensions on the leakage behavior still remains to be explored and modeled. A network representation of full-wave mode-matching method employing the metal modes is applied to the investigation of the leaky wave. The effects of metal thickness, conductivity and finite substrate width on leaky waves are discussed. Furthermore, a printed transmission line of finite-width configuration may exist the characteristic of multimode propagation. Such effect degenerates the performance of the integrated circuits. This thesis presents theoretical and experimental results for a finite-width conductor-backed copla -nar waveguide (FW-CBCPW). The guiding characteristics of FW- CBCPW are investigated first by the rigorous method of mode matching. A FW-CBCPW through line is then placed within a test fixture commonly used in laboratories, and the scattering para- meters of the through line are obtained theoretically by appro- ximating the FW-CBCPW as a simple system of coupled transmission lines. Experimental results are shown to agree very well with the theoretical ones. Finally, a technique of mode suppre- ssion isintroduced in this thesis. The connection of the side planes of the FW-CBCPW to the ground through lateral walls suppresses the undesired microstrip-like (MSL) mode and provides a wide frequency range over which the single- mode propagation occurs. The leakage or resonant phenomena of the higher-order modes can be avoided, if the distance separating the lateral walls is carefully designed.