An Ultra-Wideband-Inspired System-on-Chip for an Optical Bidirectional Transcutaneous Biotelemetry

This paper describes an integrated communication system, implementing a UWB-inspired pulsed coding technique, for an optical transcutaneous biotelemetry. The system consists of both a transmitter and a receiver facilitating a bidirectional link. The transmitter includes a digital data coding circuit and is capable of generating sub-nanosecond current pulses and directly driving an off-chip semiconductor laser diode including all bias and drive circuits. The receiver includes an integrated compact PN-junction photodiode together with signal conditioning, detection and digital data decoding circuits to enable a high bit rate, energy efficient communication. The proposed solution has been implemented in a commercially available 0.35 μm CMOS technology provided by AMS. The circuit core occupies a compact silicon footprint of less than 0.13 mm
²
(only 113 transistors and 1 resistor). Post-layout simulations have validated the overall system operation demonstrating the ability to operate at bit rates up to 500 Mbps with pulse widths of 300 ps with a total power efficiency (transmitter + receiver) lower than 74 pJ/bit. This makes the system ideally suited for demanding applications that require high bit rates at extremely low energy levels. One such application is implantable brain machine interfaces requiring high uplink bitrates to transmit recorded data externally through a transcutaneous communication channel.