Design of a CMOS System-on-Chip for Passive, Near-Field Ultrasonic Energy Harvesting and Back-Telemetry

Abstract

Many packaging and structural materials are made of conductive materials such as metal or carbon-fiber composites, which limits the use of embedded radio frequency-based telemetry systems for sensing. In this paper, we present the design of a complete passive ultrasonic energy harvesting and back-telemetry system that exploits near-field acoustic coupling to wirelessly transfer energy and data across conductive barriers. The use of near-field operation makes the telemetry robust to multipath reflections that occur at barrier discontinuities and robust to crosstalk when multiple sensors are simultaneously interrogated. Underlying the proposed architecture is a system-on-chip (SoC) that integrates different ultrasonic energy harvesting and telemetry modules. The operation of the system has been verified using SoC prototypes fabricated in a 0.5- $\mu \text{m}$ CMOS process which have been integrated with a piezoelectric transducer attached to an aerospace-grade aluminum substrate. Measured results show that the proposed near-field ultrasonic telemetry system can effectively operate across a 2-mm-thick metallic barrier at a frequency of 13.56 MHz with the SoC consuming 22.3 $\mu \text{W}$ of power.