應用於抑制電磁干擾與射頻干擾之電磁能隙結構

Electromagnetic Bandgap Structures for Suppression of Electromagnetic Interference (EMI)/ Radio Frequency Interference (RFI)

許文譯(Wen-Yi Hsu)

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(2015年)

https://doi.org/10.6342/NTU.2015.10204

摘要

本文提出兩種應用於抑制電磁干擾與射頻干擾之薄形電磁能隙結構。首先，我們列舉幾項現今行動裝置中常見的雜訊產生機制，且說明此類雜訊如何在微波系統造成電磁干擾或射頻干擾問題。基於行動裝置的環境，我們提出兩種可以應用於此環境之薄形電磁能隙結構。首先是用軟性印刷電路板製程之電磁能隙結構。藉由軟性電路板之可撓性，當此薄形電磁能隙結構黏貼於行動裝置中時，可以在環境中製造出尺寸極小之電磁能隙結構，其物理尺寸為5mm 15mm。根據色散關係分析，此電磁能隙結構可以對1.5秭赫茲到12.2秭赫茲的雜雜源產生超過 10分貝以上抑制效果。而針對行動裝置中最常使用的無線區域網路(WLAN)的頻段，此電磁能隙結構可以對天線之間的隔離度進行改善。根據量測結果，在無線區域網路所需之兩個頻帶，可提供天線間 30分貝隔離度改善。

其次，本文提出的第二種為使用印刷電路板之薄形電磁能隙結構。藉由使用雙層電磁能隙疊構，提出可以在行動裝置空間中使用的設計。藉由設計傳輸零點之頻率，進行頻帶合成。此結構能夠針對無線區域網路所需之兩個頻帶提供雜訊上的抑制。根據量測結果，此電磁能隙結構能夠對2.1秭赫茲到2.5秭赫茲和4.8秭赫茲到5.6秭赫茲提供10分貝以上的抑制效果。

關鍵字

電磁能隙結構 ； 電磁干擾 ； 射頻干擾 ； 無線區域網路

並列摘要

Electromagnetic interference (EMI) or radio-frequency interference (RFI) is an important issue in microwave system. In recent years, the number portable devices like smart phones and tablet PCs becomes larger and larger. In addition, the electronic components in devices need to be miniaturized and closer to each other in order to place more components inside devices. If the distance between the components decreases, EMI/RFI problem would become sever. In order to make sure that the electronic components function properly, good isolation between these components is necessary in the microwave system. In addition, many communication devices usually work at Wi-Fi bands, which operates on multiple frequency bands. Therefore, isolation of noise in multi-bands is also necessary.
Two kinds of thin EBG tape implementation are proposed to provide a good suppression on EMI/RFI noise inside portable devices.
First, a thin EBG tape is fabricated with flexible printed circuit (FPC) process. With FPC process, this thin EBG tape sticks on both side between top chassis of device and PCB, which is named as double-sided EBG tape (DS-EBG tape). DS-EBG tape is ease to assembly with other circuits. Second, the DS-EBG tape is very small (unit cell size: 5 mm 5 mm). Third, the suppression level (30 dB) for Wi-Fi bands application of DS-EBG tape is demonstrated.
Second, a thin EBG tape sticks on only single side of chassis is proposed and named as single-sided EBG tape (SS-EBG tape). SS-EBG tape can be fabricated with PCB process. By using double-stacked structure, SS-EBG tape has two bandgaps from 2.183 GHz to 2.509 GHz and from 4.798 GHz and 5.627 GHz. In Wi-Fi bands application, SS-EBG tape can provide additional 10 dB suppression level.

並列關鍵字

Electromagnetic bandgap (EBG) structure ； Electromagnetic Interference (EMI) ； Radio Frequency Interference (RFI) ； wireless local area network (WLAN)

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