吸收式共模濾波器設計

Design of Absorptive Common-Mode Filters

李柏叡(Po-Jui Li)

指導教授 ： 吳宗霖

國立臺灣大學/電機資訊學院/電信工程學研究所/博士(2020年)

https://doi.org/10.6342/NTU202000976

摘要

本論文旨在發展吸收式共模濾波器之合成方法，藉此消除差動傳輸系統中之共模雜訊，進一步的抑制電磁干擾與射頻干擾。與其他共模雜訊抑制技術相比，吸收式共模濾波器具有更好的性能，共模雜訊通過吸收式共模濾波器後會被消耗殆盡而非被反射，此一特性可以大幅降低共模雜訊激發輻射的風險。然而，目前吸收式共模濾波器的相關研究較少，加上雜訊的吸收在設計上相當困難，故共模雜訊吸收技術仍然未臻成熟且具有相當大的改善空間，此外，吸收式共模濾波器技術相較於其他共模抑制技術的效果優劣，也未曾被仔細探討或驗證。有鑑於此，本論文提出數種吸收式共模濾波器的設計方法，每種設計皆能夠具有優異的電路效能或特殊的功能，並且皆以實際量測驗證其效果。
論文之初，將先對共模雜訊在纜線連接結構附近之輻射機制進行探討與量測驗證。根據此輻射機制，筆者設計了一個用以比較吸收式與反射式共模濾波器效能差異的實驗，而實驗結果顯示，在大部分的情況下，吸收式共模濾波器的輻射抑制效能優於反射式共模濾波器。
本論文主要展示了四種吸收式共模濾波器的設計方法，提供了多種不同的特性與功能。首先提出的是三級式的吸收式共模濾波器設計，此為已發表論文中第一個能夠內嵌於印刷電路板製程的原型設計。第二，本論文提出第一個無電阻式的吸收式共模濾波器設計，能夠大幅降低製造成本，且因為不需表面電阻打件或電阻層的特性，能夠廣泛的適用於各種製程。接著，本論文提出雙頻帶吸收式共模濾波器的合成方法，能夠一次使兩個任意選定的頻率具有共模雜訊吸收效果，且僅需使用兩級電路架構即可完成，在共模雜訊吸收技術上為一極具突破性的發展。最後，本論文提出一種雙向吸收式共模濾波器的合成方法，此方法從最基礎的四埠網路之數學理論出發，藉由本論文提出的公式，能夠合成出效能極佳的電路，並且具有極高的設計自由度。根據此設計方法，所合成之電路的差模與共模理論上能被獨立設計，並能以各種電路元件實現，也能以各種製程製造。
本論文中，所有設計的測試樣品皆有被實際製造與完整量測。在所有已發表的吸收式共模濾波器中，本論文提出的雙頻帶吸收式共模濾波器之樣品具有最寬的雜訊吸收頻寬，而雙向吸收式共模濾波器之樣品具有最佳的效能。

關鍵字

吸收 ； 共模 ； 電磁干擾 ； 射頻干擾 ； 纜線連接結構 ； 輻射 ； 耦合式共振器 ； 印刷電路板 ； 積體被動元件 ； 差動訊號傳輸 ； 眼圖

並列摘要

This doctoral dissertation is dedicated to developing novel methods of synthesizing absorptive common-mode filters (A-CMFs), which can eliminate common-mode (CM) noises in differential signaling systems and further suppress electromagnetic/radio-frequency interferences (EMI/RFI). Compared with other CM suppression techniques, A-CMFs can provide a better performance. The CM noises passing through an A-CMF will be dissipated instead of being reflected, which largely reduces the risk of undesirable radiation. However, the development of A-CMF is still immature because of the lack of related literature and the design difficulties of noise absorption. Also, its performances compared with other CM suppression techniques have never been investigated before. In this dissertation, several methodologies that can systematically synthesize A-CMFs with good performances or special functions are proposed, which are all verified by measurements.
In the beginning of this dissertation, the mechanism of CM-induced radiation at the cable-attached structures are studied and verified by measurements. Based on this mechanism, an experiment is designed to compare the performances of A-CMF and R-CMF, and the results show that A-CMF is better than R-CMF in most of the cases.
In the main part of this dissertation, four methods of designing A-CMFs with different functions are demonstrated. First, a three-stage A-CMF is invented, being the first prototype that can be embedded in printed-circuit boards (PCBs). Second, a method of synthesizing resistor-free A-CMFs is proposed, being a very cost-efficient design that can easily adapt to different fabrication processes without using surface-mounted devices (SMDs) and resistive layers. Then, a method of synthesizing dual-band A-CMFs is proposed, indicating that two arbitrary CM absorption bands can be obtained using only two stages of circuits, which really makes great progress on the CM suppression technique. Lastly, a method of synthesizing bidirectional A-CMF is invented. This method starts from the basic math of four-port networks, providing very good performances and high design flexibility. Using this method, the design of DM and CM can be separated theoretically, and it can be realized by any circuit elements and implemented by any fabrication processes.
Test samples of the all proposed designs are fabricated and measured. The sample of the dual-band design has the broadest absorption band, and the bidirectional design gets the best figure of merit (FoM) among all the published A-CMFs.

並列關鍵字

Absorption ； common-mode (CM) ； electromagnetic interference (EMI) ； radio-frequency interference (RFI) ； cable-attached structure ； radiation ； coupled resonator ； printed-circuit board (PCB) ； integrated passive devices (IPD) ； differential signaling ； eye diagram

參考文獻

[1] S. H. Hall and H. L. Heck, Advanced Signal Integrity for High-Speed Digital System Design. Hoboken, NJ, USA: Wiley, 2009.

[2] T.-L. Wu, F. Buesink, and F. Canavero, “Overview of signal integrity and EMC design technologies on PCB: Fundamentals and latest progress,” IEEE Trans. Electromagn. Compat., vol. 55, no. 4, pp. 624–638, 2013.

[3] C. R. Paul, Introduction to Electromagnetic Compatibility, 2nd ed., NY, USA: Wiley, 2006.

[4] C. R. Paul, “A comparison of the contributions of common-mode and differential-mode currents in radiated emissions,” IEEE Trans. Electromagn. Compat., vol. 31, no. 2, pp. 189–193, May 1989.

[5] P. Fornberg, M. Kanda, C. Lasek, M. Piket-May, and S. H. Stephen, “The impact of a non-ideal return path on differential signal integrity,” IEEE Trans. Electromagn. Compat., vol. 44, no. 1, pp. 11-15, Feb. 2002.