A SENSITIVE DETECTION METHOD FOR CAPACITIVE ULTRASONIC TRANSDUCERS

We report a sensitive detection method for capacitive ultrasonic trans ducers. Detection experiments at 1.6 MHz reveal a minimum detectable d isplacement around 2.5 x 10(-4) Angstrom/root Hz. The devices are fabr icated on silicon using surface micromachining techniques. We made use of microwave circuit considerations to obtain a good displacement sen sitivity. Our method also eliminates the dependence of the sensitivity on the ultrasound frequency, allowing the method to be used at low au dio frequency and static displacement sensing applications. (C) 1998 A merican Institute of Physics.