中文摘要：

本文提出一种基于导纳矩阵的三端ElT型接头高精度超宽带等效电路参数提取方法．并将传统T型接头结构改进为凹．T型接头（concave）和凸-T型接头（convex）两种形式，以精确控制T型接头中心处寄生电容的影响．最后，在分析不同三端口T型接头连接方式对其等效电路及寄生电容影响的基础上，将改进后的T型接头结构用于研制一个中心频率12GHz高性能分支线耦合器．实测结果表明，在中心频率处该耦合器各端口的回波损耗和端口隔离度均小于一26dB，总插入损耗小于1．0dB，幅度差别小于0．1dB．

英文摘要：

In this paper,analysis of three-port T-junction based on the admittance matrix is presented. This method extracts parameters of the equivalent circuit model with high accuracy in ultra wideband. In order to control the effect of the parasitic capaci- tance, two improved T-junctions with concave and convex segments are proposed. The effect in the equivalent circuit model and par- asitic capacitance due to different connection ways of three-port T-junction is also investigated. Then the improved T-junctions are applied to design a high-performance branch-line coupler with center frequency of 12GHz. The return loss and isolation are both better than - 26dB at the center frequency, while the total insertion losses are below 1 dB and amplitude imbalance is within 0. ldB.