Giga赫茲橫向電磁波傳輸室應用在電磁干擾量測之研究

EMI Measurement Technique Investigation Using Gigahertz Transverse Electromagnetic Cell

丁惠玲(Hui-Ling Ting)

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(2008年)

https://doi.org/10.6342/NTU.2008.01909

摘要

有鑑於國內一般從事電磁波干擾（Electromagnetic Interference）量測之試驗室試驗人員對半電波暗室之替代設備－Giga赫茲橫向電磁波傳輸室（GTEM Cell）之理論並不十分清楚，且對該設備使用及可量測範圍亦不熟悉；本文從該設備原理推導出發，並依據原理撰寫換算出遠場輻射電場值之應用程式，該程式可將從頻譜分析儀直接讀取得到之電壓數據換算為三米或十米處的電場值，模擬電波暗室及開放場量測，解決廠商開發軟體需透過通訊介面（GPIB）使用及有使用頻率限制等問題。
接著驗證該設備量測電磁干擾輻射理論之準確性，並由結果了解該設備可使用的頻段及適用之待測物。首先使用電磁模擬軟體HFSS模擬一兩層金屬板之待測物總輻射量，頻段由1GHz到6GHz，並與Giga赫茲橫向電磁波傳輸室量測換算所得之待測物總輻射量作比較，得到良好的相符性，了解Giga赫茲橫向電磁波傳輸室在頻率達6GHz時，尚可在誤差範圍內，測量到待測物總輻射量。第二部分使用標準待測物－梳型信號產生器（Comb Generator）作Giga赫茲橫向電磁波傳輸室、三米、十米半電波暗室數值比對，結果得到良好相關性。
最後待測物選用具有週期性電磁能隙結構的兩層金屬板，分析其對電磁波輻射的抑制效果；並在1GHz到10GHz的頻帶，作量測和模擬的比對，結果相差值較前一待測物（兩層金屬板）稍大，本篇論文也針對相差之原因作探討。雖然量測和模擬之間存在一些差異性，但兩數列仍在同一數量級範圍內。若以實驗室研究方便性之考量，仍可用Giga赫茲橫向電磁波傳輸室進行如電路板等待測物的電磁輻射量測，概略了解電路板的輻射情形，供研究修改階段之參考；如此，僅須於最後階段再到半電波暗室或開放場進行標準測試。

關鍵字

電磁干擾 ； 橫向電磁波傳輸室 ； 待測物總輻射量

並列摘要

This thesis includes the theory derivation of the EMI measurement while using the GTEM Cell as a measuring apparatus and discusses the inaccuracy of the theory. Based on the theory we try to develop a novel program to solve the problems that are originated from the commercial program’s limit of the working frequency and measurement setup.
We validate this theory through the use of simulation software and semi-anechoic chambers (SAC). It’s not possible to validate algorithms along with voltage simulation while simulation of total radiated power on the contrary is a good way. Comparing the data, simulating from the total radiated power values is more direct and efficient than simulating the voltages according to the algorithm derivation. Besides it needs only a personal computer and lower memory requirement and save time. The validation results clearly show the performance for emission testing of the GTEM cell, especially in high frequency.
Three different objects are used as the equipment under tests (EUT). The first EUT is a bare board. We compare the total radiated power values that obtained from GTEM cell and HFSS simulation with frequency ranging from 1GHz to 6GHz.
The second EUT is a comb generator in both GTEM cell and 3m/10m chamber. We foresee the data from both tests should be corresponding because the comb generator radiates like a dipole. The results correspond with our anticipation.
For the final test, a board with EBG structure is used as the EUT. We research the EMI performance with frequency ranging from 1 GHz to 10 GHz. We also make a comparison of total radiated power values that gained from GTEM Cell and Ansoft HFSS simulation. The result somewhat is not as ideal as the former two EUTs. But the difference is considered within a reasonable range.

並列關鍵字

EMI ； GTEM ； semi-anechoic chambers ； total radiated power

參考文獻

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