消除電纜線屏蔽導體上雜訊電流之非鐵磁性共振式抑制器

Resonator-Based Ferrite-Free Chokes for Suppressing Noise Currents on Cable Shielding

曾英誠(Ying-Cheng Tseng)

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(2016年)

https://doi.org/10.6342/NTU201603817

摘要

本論文旨在發展新型雜訊電流抑制器，以有效解決電纜屏蔽導體上雜訊電流造成的千兆赫茲電磁及射頻干擾問題。相較於傳統廣泛使用的鐵磁材料雜訊電流抑制器，本研究提出的多種非鐵磁性共振式抑制器具有更高的雜訊抑制能力、吸收能力與設計靈活性。由於傳統鐵磁材料抑制器較無系統性的設計方法，並且傳統量測方法難以驗證雜訊電流抑制器於千兆赫茲時的響應。有鑑於此，針對非鐵磁性共振式抑制器設計，本論文提出完整的設計流程，並詳細探討其量測驗證方法與運用於實際情況的抑制效果。
本文根據模擬電磁場傳播於電纜線屏蔽導體的分布狀況，建立對應的模擬環境設定。利用此模擬環境，方能開始進行新型抑制器的設計。首先，藉由環繞多個共振器於電纜屏蔽導體外圍，完成非鐵磁性抑制器的設計單元。此設計單元透過磁耦合機制，得以完全反射屏蔽導體上的雜訊電流。利用串接此設計單元，本論文提出一個具有三階帶拒濾波器響應的非鐵磁性抑制器操作於2.6千兆赫茲。經由實驗驗證，此抑制器可抑制36 dB的雜訊電流並具10.8%的10 dB操作頻寬。
接著，經由參考並改良傳統的T型衰減器電路模型，本論文提出具備吸收雜訊功能的非鐵磁性抑制器，並經由驗證證明其吸收量可達97%於2.5千兆赫茲，並具有6.5%的10 dB操作頻寬。透過將此設計單元加上表面接著電阻元件並適當選擇電阻值，可自由控制其雜訊吸收量。此外，經由量測並分析電纜屏蔽導體上的雜訊電流波型分布，本論文提出一種方法可萃取電纜屏蔽導體上待測物的散射參數(S-parameters)，並用來驗證吸收式的非鐵磁性抑制器響應。
有別於前，為了拓展操作頻寬，本論文再提出一採用電耦合機制的新設計單元，並實現具備單方向吸收式功能的非鐵磁性抑制器設計。其操作原理與所需電阻元件數均大幅簡化。根據量測結果，此設計的10 dB操作頻寬可達18.8%，並有94.5%吸收量。上述所有設計皆於雜訊電流抑制與輻射抑制的量測環境下驗證。其中，三階帶拒濾波器與吸收式非鐵磁性抑制器運用於USB 3.0連接線的雜訊電流抑制響應，皆大幅優於市場上的鐵磁性材料抑制器。

關鍵字

鐵磁性 ； 非鐵磁性 ； 雜訊電流 ； 抑制器 ； 吸收式 ； 帶拒濾波器 ； 衰減器 ； 散射參數 ； 電纜屏蔽 ； 輻射抑制 ； 電磁耦合 ； 千兆赫茲 ； 電磁干擾 ； 射頻干擾

並列摘要

This doctoral dissertation is dedicated to developing novel types of ferrite-free chokes which provide efficient solutions for suppressing electromagnetic/ radio-frequency interferences (EMI/RFI) in gigahertz (GHz) ranges. Compared with traditional ferrite-material-based chokes widely utilized for passing EMI regulations, the proposed ferrite-free chokes (FFCs) feature higher suppression and design flexibility. The complete systematical design procedures, measurement methodologies, and practical verifications are studied and discussed in this dissertation.
Firstly, a simulation environment is established according to the electromagnetic field distributions on the cable shielding of a cable-attached structure. With the assistance of this simulation setup, the developed noise-current chokes are able to be designed and studied in detail. A novel resonator-based unit cell, based on magnetic-coupled mechanism, is then proposed utilizing multiple coupled resonators to uniformly surround cable shielding. When the resonances occur, cable noise currents can be eliminated through magnetic coupling between the cable shielding and surrounded resonators. By cascading three unit cells, the response of a third-order bandstop filter is realized. Compared with traditional ferrite chokes, the FFC are able to highly suppress noise currents at a specified GHz frequency band.
Furthermore, ferrite-free absorptive chokes (FFACs) are proposed for absorbing nose currents instead of reflecting it. Inspired by a traditional T-type attenuator, the FFACs are implemented based on the FFC by adopting surface-mount-device (SMD) resistors. Current-distribution experiments are performed for extracting the corresponding S-parameters of the proposed chokes on cable shielding. On the other hand, by utilizing these FFACs on commercial USB 3.0 cables, the high-level suppressions of noise currents are experimentally verified.
At last, a unidirectional electrical-coupled absorptive choke (U-EAC) is proposed. The operation concept is much more straightforward compared with the FFACs. The performance of the U-EAC is comparative with those of the FFACs but the requirement of SMD resistors is reduced significantly. All designed chokes are measured and the results demonstrate that the proposed novel chokes indeed own the capabilities of high-level suppressions and absorptions.

並列關鍵字

absorption ； noise current ； electromagnetic interference (EMI) ； radio-frequency interference (RFI) ； cable shielding ； high speed ； ferrite ； chokes ； coupled resonators ； attenuators ； surface mount device (SMD) ； electrical coupled ； magnetic coupled

參考文獻

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