Theory and performance of perpendicular diffraction delay lines

The perpendicular diffraction delay line was introduced recently as a new method for obtaining a linear variation of delay time with frequency. Basically, it consists of a transmitting array and a receiving array having elements with suitable nonuniform spacings, arranged perpendicular to each other. The dispersion arises because the effective path length of an ultrasonic beam between the input and output arrays changes with frequency. This paper presents a quantiative analysis of the perpendicular diffraction delay line together with experimental results obtained from a 2.2 Mc/s model. Also included is a complete design procedure based on interference theory. The theoretical analysis indicates that the device is capable of performing satisfactorily in any frequency range with fractional bandwidths up to 50 per cent. Measurements made on the experimental model are in good agreement with the theory.