Wireless Excitation and Electrical Impedance Matching of Piezoelectric Wafer Active Sensors

Abstract

Wireless ultrasound inspections using Piezoelectric Wafer Active Sensors (PWAS) are attractive for Structural Health Monitoring (SHM). However, the impedance mismatch between the PWAS and the wireless transponder reduces the wirelessly transmitted signal strength. Electrical Impedance Matching (EIM) circuit can be introduced to maximize the power transmission between the PWAS and the wireless transponder. This paper discusses the wireless excitation of ultrasound as well as the design, simulation, and characterization of the EIM networks for PWAS. To maximize power transmission, a two port EIM network was developed using a computerized smith chart. The equivalent circuit of the PWAS and the EIM network were then combined to establish the equivalent circuit of the matched transducer. Computer simulations were carried out to evaluate the gain, the bandwidth, and the sensitivity of the EIM networks. Two-port EIM networks were implemented for both the actuator and the sensor in an ultrasound pitch-catch inspection system. The performance of the pitch-catch systems with and without the EIM networks was compared. Detailed analysis, simulation, hardware implementation, and measurement results are presented.