A 50-mm² Crystal-Free Bidirectional WPDT System with Carrier-Reuse Clocking for Implantable Neural Interfaces

Neural implants require compact and energy-efficient wireless power and data transfer (WPDT) while avoiding reliance on costly on-board clock sources. This work presents a crystal-free, full-duplex WPDT link that reuses a 500-MHz power carrier as the sole system clock for synchronized downlink and uplink telemetry. A clock-data recovery (CDR)-less coherent ASK downlink achieves 5 Mb/s, while maintaining uninterrupted power transfer through a 6-mm implant loop. The recovered 500-MHz carrier also wirelessly locks a fast-settling UWB PLL, enabling a duty-cycled uplink supporting 5-500Mb/s. Burst-mode operation enables data-rate-scalable uplink power, ranging from 0.23 mW at 5 Mb/s to 4.93 mW at 500 Mb/s, and extends the uplink range to 40 cm using an on-chip antenna. The complete system, including the loop antenna and chip, occupies 50 mm2.