電磁波遮蔽材料及吸波材料頻率特性之探討

The Study of Frequency Properties of Shielding and Absorptive Material for Electromagnetic Wave

林振豐(Cheng-Feng Lin)

指導教授 ： 林啟瑞 ； 蘇春熺

國立臺北科技大學/機電學院/機電整合研究所/碩士(2007年)

https://doi.org/10.6841/NTUT.2007.00371

摘要

本研究主要以使用同軸導波管之Ｓ參數法由網路分析儀 (Network Analyzer)量測出S11(反射特性)與S21(透過特性)，對金屬遮蔽材料及磁性吸波材料的電磁波防制效果和相關的高低頻特性做分析，以期在我們做EMI電磁干擾對策時能夠更清晰明瞭當遭遇不同頻率的干擾時，如何交互應用金屬遮蔽方法和磁性材料吸波方法，一般產業界的EMI工程師在實務上做對策時總是不斷的摸索(Trial and Error)去做非常費時的實驗，如能對金屬遮蔽材及磁性吸波材的特性有一個清楚的了解，較能很快的找到應用的對策。
由實驗量測的結果發現，在金屬遮蔽材料的S11與S21曲線得知，在低頻及中高頻時金屬遮蔽材料有很大的屏蔽效果，尤其在500MHz以下的頻段，但在其之後的較高頻段就很難防制得了，因為屏蔽的方法是靠電磁波的反射去吸收能量。
在此實驗中，磁性吸波材料在1GHz~3GHz的頻段仍有很好的吸波效果，而且磁性材料的透射能量曲線隨著頻率越高而遞減，所以可以看出在針對高頻的對策是非常需要仰賴磁性吸波材料的高頻吸波特性。

關鍵字

電磁干擾 ； 電磁波 ； 遮蔽 ； 屏蔽 ； 吸波

並列摘要

This study investigates the shielding effect and frequency property for electromagnetic interference prevention of metal shielding materials and magnetic absorptive materials.
We use coaxial transmission line method and network analyzer to measure the S11 and S21 parameter of these materials.
The results show that the metal shield (Al) provides a better shielding effect at low frequency about lower than 500MHz, but the shielding effect at high frequency was decreasingly. Furthermore, the magnetic absorptive material (Ferrite) provides a better shielding effect at the high frequency even higher than 2 GHz.
Shielding and absorption are the best two ways to prevent EMI problem. The metal shields rely on the reflection effect to reduce the EMI energy. The ferrite material relies on the absorption effect to reduce the reflection wave from metal shield.
We can conclude from these observations, a good EMI countermeasure should be reciprocal action for different frequency band of electromagnetic wave.

並列關鍵字

EMI ； shielding ； absorption ； electromagnetic wave

參考文獻

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