Resonances of surface-bonded piezoelectric wafer active transducers and their effects on the S0 pitch-catch signal

Surface-bonded piezoelectric wafer active transducers (PWaTs) are frequently used for ultrasound generation and sensing in Structural Health Monitoring (SHM) applications. In this paper, the scattering parameters of an ultrasound pitch-catch system are analyzed to show that the surface-bonded PWaTs act like a resonator and their resonance could cause the fundamental symmetric (S0) mode pitch-catch signal to deviate from the applied excitation signal. A simulation model was implemented to reproduce the measurement results and to gain physical insights of the experimental observations. This study suggests that the excitation frequency should not overlap the resonance frequency in order to avoid the deviation of the S0 pitch-catch signal from the excitation signal.