Design of a Dual-Mode Coil-Reuse Data Acquisition System for Miniaturized Wirelessly Powered Biopotential Sensing Nodes

This work introduces a novel coil sharing technique to implement small form factor wirelessly powered biopotential recording systems. Coil used for wireless power transfer is shared with a power oscillator to transmit an on-off keying uplink signal at the same frequency as wireless power transfer (40.68 MHz) when the power signal is turned off for a short time, forming a single-coil, bidirectional, and synchronized data acquisition system. The designed batteryless system drains a current of 1.2 to 16.9 μA from a 1.1 V harvested voltage when data rate varies from 1 to 20 kbps. A prototype of the proposed design is fabricated in a 180-nm CMOS process and packaged on a compact circular board (5 cm diameter), which achieves a powering and uplink distance of 20 cm and 15 cm, respectively.