High Directivity Microstrip Directional Coupler with Tuneable Transmission Zeros

• Main Authors: Lin, Chih-Ming, 林志銘
• Other Authors: Kuo, Jen-Tsai
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/09513479809346488045

碩士 === 國立交通大學 === 電機學院碩士在職專班電信組 === 99 === This thesis presents design of a high directivity coupled microstrip directional coupler with tuneable transmission zeros. The circuit consists of two quarter-wavelengh parallel-coupled-lines and a third-order bandpass filter. An isolation zero is devised to improve the directivity of the coupler at the center frequency. In addition, a pair of tuneable transmission zeros are created at the coupled port. The control of these two transmission zeros is achieved by adjusting the line impedance of the short-circuited stubs of the filter.Corrugated microstrip coupled-lines are synthesized to equalize the phase velocities of the odd and even modes. It can significantly improve the rejection of the microstrip coupler in the upper stopband. Five circuits are fabricated and measured to verify the idea. Measurement and simulation results show good agreement.