Electric field control for capacitive micromachined ultrasound transducers

摘要

Alternating the polarity of the bias voltage in synchrony with the transmit period avoids dielectric and transformer polarization and allows the bias to be changed without generating a pressure artifact as the bias is changed. Alternating the bias polarity may also reduce the bandwidth requirements for square-law operation with low harmonic distortion, allowing more narrow band transmit excitation. Phase-inversion techniques for harmonic or other imaging may be used with a CMUT.