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

Abstract

This paper presents the first 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. The measured channel loss characteristic is smaller than 40dB within $10 \sim 40$ MHz band when the implanted depth is no more than 10cm. Injection locking (IL) based frequency-to-amplitude (F2A) conversion demodulator is proposed in RX to handle large frequency variations of TX FSK signals due to the lack of off-chip reference. The implanted TX only requires two off-chip components, micro battery and tiny probes, achieving packaged size of $7 \times 7 \times 2$ mm3. The in-body TX consumes only $8.6 \mu \mathrm {W}$ at 500 kb/s while the on-body RX consumes $591.5 \mu \mathrm {W}$. The TX power are $8 \times $ lower than previous works and achieves energy efficiency at 17.2pJ/b with minimal bill of material (BOM).