應用於RFID系統之電磁波吸收材料

Electromagnetic wave absorbing materials applied to RFID system

詹景盛(Jing-Sheng Jan)

指導教授 ： 蘇春熺

國立臺北科技大學/機電學院/製造科技研究所/碩士(2010年)

摘要

雖然RFID系統已成功的應用在我們的日常生活中，但RFID系統有其有限的應用範圍，當Tag是貼附在金屬版面上時，就很有可能發生Reader接收不到的現象，大大縮減應用範圍。但如果能透過一種吸波材料來阻隔金屬表面的反射，打破金屬物干擾間隔閡，對於RFID的應用範圍的提升必定大有幫助。本研究利用高分子混摻法(polymer blending Method)，將聚乙烯醇(Polyvinyl Alcohol)做為膠黏劑混合吸波材，製備成具有電磁波吸收效能之PVA複合薄膜。藉由導電性填充物和導磁性填充物將電磁波轉換成熱消散掉。透過塗佈方式製備出導電性及導磁性複合薄膜。依據美國材料工程協會(ASTM 4935-99)標準規範所訂定同軸導波管法配合安捷倫網路分析儀(300kHz~3GHz)之方式檢測電磁波吸波材之吸收效益。
研究結果顯示在厚度0.25mm以導磁性複合材Fe2O3(15% vol.)+CI(10% vol.)和導電性複合材石墨(15% vol.)+CI(10% vol.)於UHF RFID頻段922MHz~928MHz皆有90%之電磁波吸收效益，且隨著厚度增加至1mm可再提升至95%；並且配合HFSS模擬當標籤貼附吸波材於金屬表面，電場及磁場分佈情形可使天線接收到訊號，再透過實際量測RFID有效讀取距離，量測顯示出兩種高達95%吸收效益之導電性及導磁性複合材料，讀取距離相對也比較遠可達到780 mm及800 mm，證明電磁波吸收效益越高可使RFID標籤有效讀取距離越遠。最後在以節省吸波材成本為前提下，訂定出最佳吸波材尺寸大小，導磁性複合材為(120 mm × 50 mm)，而導電性複合材為(140 mm × 60 mm)。

關鍵字

無線射頻辨識系統 ； 電磁波吸收效益 ； 聚乙烯醇 ； 氧化鐵 ； 石墨

並列摘要

Although RFID systems have been successfully applied in our daily lives, but it’s limited range of applications. When Tag affixed to the metal version of the surface, it is very possible the phenomenon of signal reception not significantly reduce the scope of application. If the metal surface through the absorbing material blocking the reflection of electromagnetic wave(EMW), interference to break the metal to enhance the application of RFID will be useful. Use of polymer blending Method to Polyvinyl Alcohol (PVA) as a mixed-adhesive absorbent was prepared with the absorption of EMW performance of PVA composite films. Use of conductive filler body impedance of free electrons accelerated in the EM field to the resistance of materials under the collision to stop and generate heat within the lattice to consume EMW. Permeability filler because the magnetic field generated by the hysteresis effect of spin into heat, so that EMW absorbing material is dispersed to the inside. According to the American Materials Engineering Society (ASTM 4935-99) testing standards set the absorption efficiency of EMW absorbing materials.
It shows that permeable composite film Fe2O3(15% vol.)+CI(10% vol.) and conductive composite film graphite(15% vol.)+CI(10% vol.) at 0.25mm possess 90% electromagnetic absorption under UHF, and it can be raised by 5% as thickness increases to 1mm. At the meantime, HFSS is introduced here to simulate the electromagnetic field as RFID tag applied to metal material, then practical reading distance of permeable composite film and conductive composite film are measured respectively. The result of conductive composite film is 780mm and permeable composite film is 800mm. It can be proven that materials with better electromagnetic absorption could resist the interference of metal material. So, based on the cost basis, the dimensions of absorption materials are 120mm×50mm and 140mm×60mm, permeable composite film and conductive composite film respectively.

並列關鍵字

RFID ； Electromagnetic absorb Effectiveness ； Polyvinyl Alcohol ； Ferric Oxide ； Graphite

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