A novel structure of a near-field communication (NFC) loop antenna for mobile phones with a metal back case is proposed. The proposed structure of the metal back case itself can operate as an NFC loop antenna through the design of a simple single turn loop antenna on the top portion of the metal back case, so that the simple structure of the proposed NFC loop antenna can reduce the overall thickness of the NFC antenna for slim mobile phones. Since a sintered ferrite sheet with generally higher relative permeability (μr ≈ 200) must be used to reduce the performance deterioration of the conventional NFC loop antennas due to the eddy current in the battery pack of a mobile handset, the cost of these conventional NFC antennas is high, and they are considerably fragile. In this paper, the proposed NFC antenna is designed without the ferrite sheet and in the optimal location to ensure minimum interference from the adjacent metallic components.
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