Miniaturized Dual-Loop NFC Antenna With a Very Small Slot Clearance for Metal-Cover Smartphone Applications
A near-field communication (NFC) dual-loop antenna with a miniaturized size of <inline-formula> <tex-math notation="LaTeX">$15\,\, \text {mm} \times 25 \,\,\text {mm}$ </tex-math></inline-formula> is initially proposed for full metal-cover smartphone applications. To achieve a small clearance zone on the metal cover, a small rectangular slot of size <inline-formula> <tex-math notation="LaTeX">$8 \,\,\text {mm} \times 16\,\, \text {mm}$ </tex-math></inline-formula> is loaded into the metal cover. To allow good inductive coupling, the NFC antenna is only 0.37 mm beneath the center of the rectangular slot. Because of that, the direction of the eddy current induced on the metal cover will be the same as the dual-loop NFC antenna. It is noteworthy that the prototype NFC antenna integrated with a single rectangular slot loaded full metal cover was certified by the Europay, MasterCard, and Visa test.