An analysis of coupled transmission lines with tapered transitions

✍ Scribed by Takashi Nakamura; Shingo Matsuura; Hiroshi Kimura

• Publisher: John Wiley and Sons
• Year: 2000
• Tongue: English
• Weight: 337 KB
• Volume: 83
• Category: Article
• ISSN: 8756-663X
• DOI: 10.1002/(sici)1520-6432(200003)83:3<26::aid-ecjb4>3.0.co;2-d

✦ Synopsis

One of the factors responsible for cross-talk, that is, the unnecessary coupling between transmission lines, are tapered transitions of coupled transmission lines. This article presents an analysis and experimental data on the transmission characteristics of the coupled transmission lines considering the transitions. Applying the traveling wave mode method, the distributed quantities for the even and odd modes of the traveling wave are determined, so that they indicate the unnecessary coupling in the transitions. Then, the four-port S parameters are determined for the coupled transmission lines, which represent the following characteristics: matching, coupling (near-end cross-talk), transmission, and directivity (far-end cross-talk). The result is compared to the results of the conventional method, where the coupling in the transition parts is ignored. It is revealed by these analyses that the transmission characteristics depend on the taper angle of the transitions and do not agree with the results given by the conventional method. It is also shown that the tapered structure is responsible for the incomplete directivity. An experiment is also performed, and the results agree well with the results of theory. In other words, the validity of the method presented in this article is demonstrated.