Analysis of wireless powering of mm-size neural recording tags in RFID-inspired wireless brain-machine interface systems

This paper provides a full analysis of powering mm-size cortical implants wirelessly. An effective approach for wireless power and data transfer in neurorecording microsystems is the backscattering-based RFID-inspired communication. In this mechanism, an external interrogator powers the implant unit by microwave radiation power, and the implant IC superimposes the neurosignal on top of the signal backscattered to the interrogator. This paper characterizes wireless RF link between an external transmit antenna and an implantable antenna using the two-port model. It presents the design of a novel 1-mm³ implantable loop antenna and four different external loop antennas with various features to analyze aspects and factors limiting the wireless power transfer.