Wireless charging receiver coils and specific absorption rate (SAR)/ proximity sensors both require relatively large surface areas to function. In addition, there are limits on the kinds of materials that can be placed around these components. Current implementations for wireless receiver coils and SAR sensors are separate and discrete. In consumer devices such as smartphones and smartglasses, components are tightly packed, such that these sensors fight for space; improving one is to the detriment of the other. This disclosure describes an integrated wireless power receiver and capacitive SAR sensor using two concentric coils in the same area of a flexible printed circuit board. The capacitive SAR, which requires two sensor pads, is made operative by having each coil act independently as one of the two sensors. The wireless power receiver is made operative by switching together the two coils to function as a single coil, thereby increasing their current-carrying capacity.
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Isaacs, Philip; Xu, Kai; and Stephanou, John, "Combined Wireless Power Receiver and Capacitive Sensor", Technical Disclosure Commons, (February 23, 2023)