An Extremely Wideband Common-Mode Filter Using Second Order Transmission Zero of Magnified Coupled Defected Ground Structure

• Main Authors: Chih-Ping Chen, 鄭至斌
• Other Authors: Ding-Bing Lin
• Format: Others
• Language: zh-TW
• Published: 2018
• Online Access: http://ndltd.ncl.edu.tw/handle/bmr5w8

碩士 === 國立臺北科技大學 === 電子工程系 === 106 === In this paper, we propose an extremely wideband common-mode band-stop filter for high-speed differential signals. The proposed design is realized by using second order transmission zero, which is generated from the magnified coupled defected ground structures (DGSs), to reach the wideband common-mode noise suppression. Moreover, the proposed structure is fabricated on printed circuit board (PCB) with low cost and simple manufacturing process, and the equivalent circuit model of the proposed DGS resonators, are also constructed to predict the phenomenon of the common mode stopband. By observing the full-wave simulation and measured result, the differential-mode insertion loss is within -5dB form DC to 10 GHz. Common-mode noise can be reduced over 10 dB from 3.1 GHz to 15.5 GHz in the frequency domain, and approximately 63% of amplitude in the time domain. The differential eye diagram measurement also proves the differential signals retain good quality of transmission. These results show that the proposed common-mode band-stop filter can effectively suppress the common-mode noise with broadband characteristic, and keep good differential signal integrity at the same time. Additionally, the fractional bandwidth of the common-mode stopband can achieve 133%, and the filter size is only 0.274g x 0.284g, where g is the wavelength of the stopband central frequency. Finally, to our knowledge, this is the first common-mode filter using the second order transmission zero and magnified coupled DGS for the high-speed signals to extend the stopband. And it is also a simple geometric structure with the largest fractional bandwidth and the most compact size on a PCB.