針對近場通訊於金屬背蓋環境之天線設計

近年來，由於行動通訊技術的發展與演進，使得電信相關產業得以蓬勃發展，其中，行動通訊技術又可分為長距離無線通訊技術與短距離無線通訊技術兩大類，而近場通訊則是屬於短距離通訊技術的範疇。本論文主要針對近場通訊在金屬環境下之影響進行研究，並提出一種新穎的設計方式，改善金屬環境對於磁場的屏蔽效應。此設計藉由在金屬外殼上切割出一條金屬隙縫，利用金屬隙縫的開路特性，改變在金屬外殼上感應電流的方向，使得反方向的感應電流減少，進而減少金屬與發射端線圈之間相互抵銷的磁場，以抑制金屬對於磁場的屏蔽能力。同時此設計藉由電流必須形成迴路之特性，使得在金屬外殼上具有與發射端線圈相同方向的感應電流，藉以提升在金屬環境下近場通訊系統的感應距離。最後，經由模擬與量測結果顯示，本論文所提出之架構可以減少金屬環境對於近場通訊發射端線圈的磁場屏蔽效應，且與自由空間中的讀取距離相比，可提升73%的讀取距離，而與其他抑制磁場屏蔽效應的架構相比，在維持相同的感應距離下，本論文所提出之設計，其發射端線圈面積只需要原先的90%，而金屬外殼上的切割面積則只需要32%，可有效縮小發射端線圈尺寸與金屬外殼的切割面積，在實務上極具其應用價值。

關鍵字

近場通訊；金屬環境；屏蔽效應；感應電流

並列摘要

The study proposes a design method of novelty to improve shielding effect of metal environment against magnetic field, specific to effect on Near Field Communication antenna under metal environment. The design is that by means of cutting out a metal slit on metal housing, with open circuit property of metal gap, to change direction of induced current on metal housing, so that induced current of reverse direction reduced, and thus mutual offset magnetic field between metal and antenna reduced, so that induced current of reverse direction also reduced, thereby shielding capability of metal toward magnetic field can be suppressed. Meanwhile the design adopts property of a current must form a loop, which makes metal housing equipped with induced current in the same direction as antenna, whereby enhances NFC read distance under metal environment. In the end, by means of simulation and measurement, the results show that the paper proposed structure is able to reduce magnetic shielding effect of metal environment against NFC antenna, and enhance scanning distance by 73%. While comparing to frameworks of other suppressing magnetic shielding effect, under the same read distance, the paper proposed design will need antenna area of 90% original required; and metal housing sectional area only needs 32%, thus able to reduce antenna size and metal housing sectional area effectively.

並列關鍵字

Near field communication ； Metal housing environment ； Shielding effect ； Induced current

參考文獻

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針對近場通訊於金屬背蓋環境之天線設計

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