NFC Loop Antenna in Conjunction With the Lower Section of a Metal Cover

This letter proposes a near-field communication (NFC) antenna for smartphones with a metal cover that includes an embedded narrow slot, therein splitting the metal cover into upper and lower sections. The proposed NFC antenna is a simple loop structure that is formed by incorporating a three-dimensional coupling strip with the upper edge of the metal cover in the lower section. Because this antenna structure can substantially reduce the eddy current, excellent inductive coupling can be achieved through the clearance zone of the narrow slot. The proposed NFC antenna is relatively thin and achieves excellent performance in the read/write mode. Furthermore, in the card emulation mode verified by Europay, MasterCard, and Visa test, it even surpasses the performance of certain other NFC antennas in smartphones with non-metal covers.