Time-Multiplexed Beam-Steering Antenna Arrays for Extended-Coverage RF Powering of Multiple CMOS Brain Implants

This letter introduces a wireless powering system for multiple implantable devices located across a wide region of the human brain, addressing the spatial coverage challenges in traditional powering methods. We present an RF phased-array time-multiplexing technique that extends the powering coverage to as far as one hemisphere. The transmitter (TX) array is designed with optimal surface currents at 915 MHz to reach and beam-steer deep brain tissue. With transmitting 1 W, this method ensures safe and consistent power delivery over 18-cm lateral span and provides at least $250~\mu $ W to 6-cm deep receiver (RX) implants. In addition, we developed a dynamically biased 65-nm CMOS rectifier, featuring peak power conversion efficiency (PCE) of 72.6% at −2 dBm input power. The integration of phased-array multiplexing and an efficient CMOS rectifier offers a pathway toward arrays of smaller, battery-free neurostimulation implants, capable of simultaneous operation under stringent safety requirements and limited wearable power source size.