A 200-Mb/s Energy Efficient Transcranial Transmitter Using Inductive Coupling

This paper presents an energy efficient wireless transmitter (TX) for neural implants. It utilizes inductive coupling with de-Q'ed TX inductor to achieve 200 Mb/s throughput. An ultra-low power injection-locked phase lock loop with background frequency calibration generates a clean 200-MHz TX clock from a 10-MHz reference. The TX chip is fabricated in TSMC 65-nm CMOS process, and the 10 x 10 mm(2) coupled inductors are implemented on two-layer printed circuit boards. A custom receiver is fabricated in the same CMOS process to facilitate measurements. The prototype transceiver achieves 5e-11 bit error rate (BER) over the 11.8-mm-thick skull of an eight-week primordial piglet carcass and <1e-12 BER over 11-mm air gap. The entire TX chip consumes 300 mu W from a single 0.5 V supply. The energy efficiency of the TX is 1.5 pJ/b.