Wire-Type Dispersive Ultrasonic Delay Lines

Ultrasonic delay lines are described which utilize the dispersion of longitudinal waves in cylindrical wires to provide a delay which is variable with frequency. Existence of an inflection point in the delay-vs-frequency characteristic for the lirst longitudinal mode allows the delay characteristics to be either approximately linear or to havpe ositive or negative curvature. By operating below the cutoff frequency for the second longitudinal mode, the unwanted responses are limited mainly to flexural modes. Various designs are described which operate in different regions of the delay-vs-frequency characteristic. One model is described which departs by ±7.5 microseconds from a linear delay slope of 1710 microseconds per megacycle over a 14 per cent band centered near 1.5 megacycles.