應用於降低電磁干擾之可拆卸共振型雜訊抑制器

Resonator-Based Noise Suppressors with Detachable Capability for the Mitigation of Electromagnetic Interference

林彥如(Yen-Ju Lin)

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/碩士(2016年)

https://doi.org/10.6342/NTU201603318

摘要

本論文旨在發展一種具有可拆卸特性的雜訊抑制器，以能夠有效阻絕金屬板上的雜訊傳播為目標。傳統上，此類問題多利用高導磁磁材料貼片作為解決方案，但該方法係利用材料特性導致的損耗吸收雜訊，因此其抑制能力受限於物質特性，並不足以完全消除高頻雜訊，而且該方法缺乏設計的自由度，難以彈性的應用於日漸複雜的電磁干擾問題；與其相較，本研究所提出的雜訊抑制技術係利用電磁共振器為原理，其具有極高的雜訊抑制能力及設計靈活性。
首先，本文根據一個常見的電磁干擾情境，將其簡化以設計一個可以定量衡量抑制器特性的測試板，該測試版主在建立環境使雜訊在單一金屬板上傳播，此設定跳脫了以往將雜訊傳播路徑設定在傳輸線或導波架構的框架，使情況更接近實際雜訊傳播的情形。除此之外，為了加速設計過程，本文提出一個系統化的方法為雜訊抑制器建立電路模型，以便之後進行電路合成。
在本論文中，反射式的雜訊抑制器是利用四分之波長共振器實現，其對雜訊的抑制能力可高達30 dB且其3-dB的雜訊抑制頻寬可達 5.7%。相較之下，商用磁性材料貼片僅能提供約3 dB的雜訊降低效果。藉此可以有效說明，利用共振器的雜訊抑制方法可以更全面而且更有效的阻擋雜訊傳播。
接著，為了完全的將雜訊消除，本文藉由兩種微波電路的原型(單方向吸收器和π型衰減器)，合成了兩種吸收式的抑制器。它們在測試板上的雜訊吸收效果，可經由電流分布(模擬)或是磁場分布(模擬及量測)的駐波比證明。換句話說，因為反射式抑制器的高反射特性，其將會有遠大於吸收式抑制器的駐波比。
最後，本文進行了使用電流分布獲取雜訊抑制器在單一金屬板上特性的相關推導，從電流分布得到的資訊，可以獲知雜訊抑制器的反射和吸收特性，亦可以推算出抑制器的反射和吸收功率。

關鍵字

電磁干擾 ； 雜訊抑制器 ； 鐵磁性材料 ； 駐波比 ； 吸收 ； 反射

並列摘要

This thesis is dedicated to the development of a new kind of noise suppressor with detachable capability to efficiently mitigate the noise transfer on metal plates. Compared with the conventional method using ferrite-based absorbers, which is inadequate to fully eliminate gigahertz (GHz) noise and lack design freedom, the proposed resonator-based technique features high-level noise rejection and design flexibility. Therefore, it is more suitable to deal with the complicated electromagnetic interferences nowadays.
First of all, a test environment to quantitatively estimate the performance of noise suppressors is constructed based on a simplified version of electromagnetic interference (EMI) scenario. The board aims to create an environment where noise can propagate on a single metal plate. This setup is different from the conventional aspect which often limits the paths of noise transfer to transmission lines or waveguides. Hence, this board is more similar to the situation in practice. And then, in order to accelerate the design process, a systematic procedure is developed by establishing circuit models for the suppressors. Subsequently, this procedure is applied to all suppressors in this thesis.
Next, reflective-type noise suppressors are studied. By utilizing λ/4 strip resonators, high-level noise suppression up to 30 dB can be achieved while the 3-dB suppression bandwidth can be up to 5.7%. In contrast to the commercial ferrite sheets, which provide merely 3-dB noise elimination, the proposed resonator-based suppressors are indeed able to block the noise transfer completely and efficiently.
Afterward, in order to entirely remove noise from devices instead of reflecting it, two absorptive-type noise suppressors (unidirectional absorber and π-type attenuator) are synthesized using classical circuit prototypes. Their absorptive effects on the test board are validated both though simulation and measurement by observing standing wave ratios (SWRs) obtained from current and magnetic field distributions. In other words, due to strong reflection, for reflective-type suppressors, their SWRs will be a lot greater compared with absorptive-type suppressors.
Finally, the derivations about how to extract the properties of suppressors on a single metal plate through current distributions are conducted. From the information provided by current distributions, the reflective and absorptive properties can be known. In addition, the reflected power and absorbed power caused by the suppressors can be calculated.

並列關鍵字

Electromagnetic interference (EMI) ； noise suppressors ； ferrite materials ； standing wave ratio ； absorption reflection

參考文獻

[1] C. R. Paul, Introduction to Electromagnetic Compatibility, 2nd ed., New York:Wiely, 2006.

[2] Intel Corporation, “USB 3.0 Radio frequency interference impact on 2.4 GHz wireless devices,” 2012.

[3] 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. 627–638, 2013.

[4] C. Y. Hsiao, C. H. Tsai, C. N. Chiu, and T. L. Wu, “Radiation suppression for cable-attached packages utilizing a compact embedded common-mode filter,” IEEE Trans. Components, Packag. Manuf. Technol., vol. 2, no. 10, pp. 1696–1703, 2012.

[5] S. J. Wu, C. H. Tsai, T. L. Wu, and T. Itoh, “A novel wideband common-mode suppression filter for gigahertz differential signals using coupled patterned ground structure,” IEEE Trans. Microw. Theory Tech., vol. 57, no. 4, pp. 848–855, 2009.