A novel method for measuring dielectric charging of CMUT arrays

A novel method to detect the bias voltage shift caused by dielectric charging in immersed CMUT arrays is proposed. The proposed method uses acoustic crosstalk as a means of coupling ultrasonic signal from the transmitting element to the receiving element, thus no additional equipment is required except the standard driving circuits and amplifiers in CMUT systems. Continuous sinusoid waves with and without dc offset were used in experiments and output signals caused by acoustic crosstalk with peak to peak amplitudes in the range of 100-200mV were observed. The calculation of bias voltage shift was illustrated graphically. The array was then intentionally charged and a change of voltage shift in the correct direction was observed using the same method. The proposed method can be modified to use unipolar square pulses, thus enabling real time monitoring and automatic calibration of CMUT arrays.