title: The characterization of capacitive micromachined ultrasonic transducers in air.
abstract: Surface micromachined, capacitive ultrasonic transducers have been fabricated using a low thermal budget, CMOS-compatible process. They exhibit interesting properties for transduction in air at frequencies in excess of 1 MHz, when driven from a standard ultrasonic voltage source. Experiments are described using 1 mm square devices in air, operating in both pitch-catch and pulse-echo modes. The dependence on d.c. bias voltage is examined, together with calibration measurements using 1/8 in. microphones. The radiated beam profile, and the farfield directivity pattern, have been measured for both broad bandwidth and one-burst excitation, using a scanned miniature receiver. A 16 element square array is also presented, which has been used to measure the beam cross-sections from a focussed source.
authors.affiliation: School of Engineering, University of Warwick, Coventry, UK. esslz@csv.warwick.ac.uk
authors.forename: J S
authors.initials: JS
authors.lastname: McIntosh
authors.forename: D A
authors.initials: DA
authors.lastname: Hutchins
authors.forename: D R
authors.initials: DR
authors.lastname: Billson
authors.forename: T J
authors.initials: TJ
authors.lastname: Robertson
authors.forename: R A
authors.initials: RA
authors.lastname: Noble
authors.forename: A D R
authors.initials: AD
authors.lastname: Jones