現今的數位訊號大部分都是使用差模訊號傳輸，然而差動走線可能會因為訊號走線不等長(Asymmetrical Routing)、轉角(Bending)、信號時序落差(Timing Skew)等等，使得差模訊號傳輸無法維持對稱性，進而產生共模雜訊(Common Mode Noise)，共模訊號藉由不理想的回流路徑而產生輻射，進而引發EMI相關問題。
因此本論文提出以串聯整合式架構的匹配網路設計雙頻吸收型共模雜訊濾波器，期望抑制、吸收實際電路上差動傳輸線等情況所引起之共模雜訊，並同時保持差模訊號的訊號完整性，便是本論文著重的研究目標。我們使用串聯的方式以及搭配E-type的RCMF，經模擬後，當設定90%吸收效率時，雙頻吸收頻寬分別在2.17~2.48GHz與4.69~5.29GHz，吸收比例頻寬在f_1的地方約12.5%左右，而在f_2的比例頻寬大約為11.7%。同時可以縮小化共模抑制濾波器的面積，將共模雜訊濾波器應用在雙頻，並使其具有良好的差分信號完整性。

Most of digital signals are using differential-mode signal to transmit nowadays. However, differential routing may cause by asymmetrical-routing, bending, timing- skew….That will make differential-mode signal transmission which cannot maintain symmetry, resulting in common-mode noise. Common-mode noise will produce radiation with poor return path, resulting in problems of EMI.
Therefore, this project proposes to design a dual-band absorptive common-mode noise suppression filter with series unified matching network, expecting to suppress and absorb the common-mode noise caused by the differential transmission line on the actual circuit. At the same time, we keep the differential signal integrity, that is the most important goal in our research. We use the way of series unified matching network and E-type RCMF.After simulation, when the absorption efficiency is set to 90%, the dual-frequency absorption bandwidth fall on 2.17~2.48GHz and 4.69~5.29GHz, and the absorption ratio bandwidth is at f_1. about 12.5%, while the proportional bandwidth at f_2 is about 11.7%. At the same time, that can reduce the area of the common-mode noise suppression filter, besides apply the common-mode noise suppression filter for dual-band, and have good differential signal integrity.

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