PHASE-CONJUGATE ARRAY FOCUSING IN A MOVING MEDIUM

Theoretical formulas are developed that demonstrate the effect of a constant convection velocity on the focusing characteristics of a phase-conjugate (or time-reversing) acoustic array. The convection velocity influences the conjugate-array focus field by displacing it relative to its location in a nonmoving medium. For a planar array and a convection velocity that is less than the acoustic speed, the focal displacement is parallel to the plane of the array, and is proportional the propagation distance and the convection-velocity component parallel to the plane of the array. The convection-velocity component perpendicular to a planar phase-conjugate array only changes the phase of the array's response. It does not influence the size or location of the phase-conjugate array's focus.