A Useful Methodology to Convert the Smartphone Metal Cover Into an Antenna Booster for NFC Applications

A useful method to transform the smartphone metal cover into an antenna booster for near-field communication (NFC) antenna installed in a full metal cover (FMC) smartphone is proposed. In this proposed work, by properly embedding a series capacitor into a meticulously selected location within the metal cover, strong coupling between the NFC antenna coil and the metal cover will be generated, which mitigates the reverse eddy current induced on the metal cover. Because of that, the performance of the NFC antenna (located below a narrow horizontal slot-loaded metal cover) is substantially improved, as compared to a reference stand-alone NFC antenna in free-space conditions. To verify this proposed methodology, an ordinary single-turn coil reference NFC antenna 1 (ref 1) and a 3-turn coil reference NFC antenna 2 (ref 2) are initially designed via simulation, followed by the conducting of several typical experiments on these two reference antennas. Finally, the two reference prototype NFC antennas that have utilized this method for a single horizontal slot-loaded FMC are also certified by the Europay, MasterCard, and Visa (EMV) test.