A 7 x 7 x 2 mm³ 8.6-μW 500-kb/s Transmitter With Robust Injection-Locking-Based Frequency-to-Amplitude Conversion Receiver Targeting for Implantable Applications

Abstract

A transmitter (TX)/receiver (RX) pair using galvanic coupling to achieve in-body to on-body body channel communication (I2O-BCC) for ultra-low power (ULP) miniaturized implanted applications is presented. The I2O-BCC enables low loss communication ( in vivo communication distance using the body as a transmission medium. Injection locking (IL)-based frequency-to-amplitude (F2A) conversion demodulator is proposed in RX. It can handle more than 20% frequency variations exhibited by the TX frequency-shift keying (FSK) signals due to the lack of accurate off-chip reference. The packaged implanted TX measures $7\,{\times }\,7\,{\times }\,2$ mm3. It contains a micro-battery, two micro-probes, and the designed SoC in 130-nm CMOS process. The in-body TX radio block consumes only 8.6 $\mu \text{W}$ at 500 kb/s with an on-chip power management unit that exhibits a 45% power efficiency, while the on-body RX consumes 591.5 $\mu \text{W}$ . The TX radio block power is 8 $\times $ lower than previous works and achieves energy efficiency at 17.2 pJ/b with minimal bill of material (BOM).