Robust Biopotential Acquisition via a Distributed Multi-Channel FM-ADC

This contribution presents an active electrode system for biopotential acquisition using a distributed multi-channel FM-modulated analog front-end and ADC architecture. Each electrode captures one biopotential signal and converts to a frequency modulated signal using a VCO tuned to a unique frequency. Each electrode then buffers its output onto a shared analog line that aggregates all of the FM-modulated channels. This aggregation results in rugged, wearable form factor by eliminating wire clutter of traditional systems. A gateway integrated circuit then digitizes the composite FM signal and transmits for further processing. The coding gain due to bandwidth expansion of FM provides a large usable dynamic range (DR) and the single ADC for multiple channels results in significant power savings. Finally, the use of FM signals between the transducers and ADC provides resilience to motion and EMI artifacts. The system is implemented in 65 nm silicon using two distinct 1 mm
²
chip designs. Six-channel operation is demonstrated using FM channels with center frequencies around 15 MHz and the system achieves a usable DR of over 100 dB, while achieving figure of merit competitive with state of the art prior works using traditional approaches.