Electronically variable time delay in ultrasonic Lamb wave delay lines

This paper is concerned with the effect of a biasing electric field on the propagation of ultrasonic Lamb waves in thin plates. The biasing field is applied parallel to the direction of substrate thickness. Since the plate is very thin, large values of electric field can be obtained with low bias voltages. Our experiments have utilized Lamb wave delay lines fabricated on a 2.5 /spl mu/m thick silicon nitride membrane. Preliminary results indicate that fractional time delay changes greater than 130 parts per million can be obtained with bias voltages less than 2 volts.