Ghost suppression in ultrasonic measurement with a sparse phased array by using frequency tuning of piezoelectric microsensors

摘要

Ghosts in ultrasonic measurement with a sparse phased array are effectively suppressed by combining directivity patterns using two frequencies. The two-frequency ultrasonic measurement can be realized by tuning the resonant frequency of piezoelectric microsensors composing the array. Piezoelectric tunable resonant microsensors have been fabricated for the measurement technique. The resonant frequency has been controlled adequately to switch between a base frequency and a lower sub-frequency of 57% to the base frequency on the fabricated sensor. The frequency switching enables the sparse phased array in the two-frequency measurement to suppress ghosts by decreasing sidelobe level from 134% to 10% compared to the conventional single frequency measurement.