Doubly steered array of modal transducers

Line or planar arrays steered to end fire generally require quarter wavelength spaced transducer elements with 90 degree sequential phase shifting to attain a unidirectional beam in an end fire direction. Half wave length element separation with 180 degree sequential phase shifts yield end fire but in both directions and at a reduced level. Part of this lower level bipolar directionality is due to the fixed broadside directionality of the transducer elements. However, use of reduced-size, leveraged-circular, acoustical-modal transducer elements, which allow incremental steering, provide a means for substantial end fire steering without the need for quarter wavelength spaced elements. In this case the elements, as well as the array, can be steered in the same direction attaining full-strength, unidirectional end fire steering at half wavelength array spacing. We present the physics of the leveraged-circular, acoustic-modal, transducers and their operation in the monopole, dipole and quadrupole modes along with their implementation and application in doubly steered arrays.