A CMOS SoC for Wireless Ultrasonic Power/Data Transfer and SHM Measurements on Structures

Abstract

This paper describes a highly-integrated CMOS system-on-chip (SoC) for active structural health monitoring (SHM). The chip integrates ultrasonic power and bidirectional half-duplex data transfer, a power management unit (PMU), and an ultrasound transceiver to enable wireless ultrasonically-coupled sensor SHM networks on structures. The PMU includes an active bias-flip rectifier with off-delay compensation, a high-efficiency dual-path DC-DC converter with inductor time-sharing, and five switched-capacitor DC-DC converters to generate multi-level spectrally band-limited pulses for guided-wave SHM. The chip was fabricated in a standard 180 nm process and has a die area of $2\times 2$ mm2. Test results show power conversion efficiency (PCE) > 85% for the active rectifier, > 70% for the inductive DC-DC converter, and > 60% for the switched-capacitor DC-DC converters. Output pulses have a peak-to-sidelobe ratio (PSL) > 30 dB and worst-case out-of-band emissions < −30 dB, respectively. The SoC was integrated with a low-power microcontroller and passive components to realize miniaturized (15 mm $\times 30$ mm) wireless SHM nodes. A set of nodes was deployed on an SHM test-bed (carbon fiber reinforced polymer sheet) representing an airframe panel. Tests on this wireless network confirm both long-range ultrasound power/data transfer and the ability to detect structural damage.

Keywords

• Energy harvesting
• structural health monitoring (SHM)
• ultrasound power/data transfer