Telemetry platform for deeply implanted biomedical sensors

This paper describes the design of low-power platform circuits for deeply implanted biomedical sensors, a bidirectional transceiver with Manchester decoder and a successive-approximation ADC. Potential operating frequencies are analyzed with respect to system limitations of power, size and complexity. It is argued that operation using low carrier frequencies provides high power efficiency while slightly increasing the size of off-chip antennas, and 125-kHz OOK and 27.12-MHz FSK are chosen for forward- and reverse-telemetry, respectively. The 8-bit SAR ADC achieves a balance between power, resolution, and sampling rate, and the scalable architecture increases its versatility. The platform circuits were fabricated in the AMI 0.5-mum process and test measurements confirm the transceiver consumes 1.05 mW while the ADC consumes 50 muW.