Multiple-frequency ultrasonic measurement for ghost suppression with a sparse phased array by frequency-tunable microsensors

An ultrasonic measurement technique has been proposed for ghost suppression with a sparse phased array by using multiple frequencies owing to frequency-tunable microsensors. A sparse phased array with an inter-element spacing over a half wavelength caused large grating lobes resulting in ghosts. In the proposed method, the ghosts have been effectively suppressed by combining with measurement at lower frequencies on a sparse phased array with reduced number of sensor element. Basic characteristics of the ghost suppression mechanism and an optimal array design are described.