Direction finding circuit arrangement

Abstract

A sonic energy scanning apparatus in which two directional primary sonic energy beams at two different frequencies are radiated into a medium capable of producing nonlinear acoustic effects to produce a third sonic energy beam having a given directional characteristic and a frequency equal to the difference between the frequencies of the primary beams. Scanning with the third beam is effected by varying the direction of the axes of, and the frequency difference between, the two primary beams in discrete steps for correspondingly varying the direction of the axis of the third beam over a selected angular sector and the frequency of the third beam such that each direction of the third beam axis is associated with a respectively different frequency, and by identifying the direction to a source of echoes of the third beam by determining the frequency of such echoes.