Dispersive delay lines using ultrasonic surface waves

Surface ultrasonic wave delay lines with dispersive time-frequency characteristics have been made using interdigital electrode arrays with variable element spacings on LiNbO3. The devices operate at 60 MHz with low insertion loss and a 3-dB bandwidth over 25 percent. A model has been devised which accurately predicts the phase and amplitude characteristics of the devices. "Weighting" the array to improve the phase characteristic is described.