Recently, technologies have arisen that allow near field coupling (e.g., wireless power transfers (WPT) and near field communications (NFC)) between portable devices in close proximity to each other. Such near field coupling functions may use radio frequency (RF) antennas in the devices to transmit and receive electromagnetic signals. Because of user desires (and/or for esthetic reasons) many of these portable devices are small (and becoming smaller), and tend to have exaggerated aspect ratios when viewed from the side. As a result, many of these portable devices incorporate flat antennas, which use coils of conductive material as their radiating antennas for use in near field coupling functions.
For example, an NFC antenna integration in a plastic chassis portable device may be achieved by creating a cutout on a conductive electromagnetic interference (EMI) coating under a palm rest area of the portable device, such that the NFC antenna that is attached to the cutout area may radiate through the chassis effectively. For devices having a complete metallic chassis, the metallic chassis is often used to maintain mechanical strength in a thin design. The use of the metallic chassis creates a key challenge for NFC coil antenna integration into such devices (e.g., thin laptop computer such as Ultrabooks), since the NFC antenna needs a non-metallic surface in order to radiate through.
Accordingly, a solution allowing the NFC antenna to be integrated into a thin metallic chassis and maintain efficiency in the NFC antenna radiation is desired so that industrial design, mechanical integrity, and customer appeal may be preserved.
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