McIntosh J S, Hutchins D A, Billson D R, Robertson T J, Noble R A, Jones A D R
School of Engineering, University of Warwick, Coventry, UK.
Ultrasonics. 2002 May;40(1-8):477-83. doi: 10.1016/s0041-624x(02)00162-2.
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.
