LOW FREQUENCY SONAR PROJECTOR AND METHOD

摘要

A low frequency sonar projector (100) for use with a projector array having at least one ceramic stack (102) comprised of lead magnesium niobate-lead titanate (PMN-PT) having a Curie temperature Tm approximately equal to the operating temperature of the projector. A mechanism (104, 106) is provided for applying heat to and for controlling the temperature of the ceramic stack (102) to within a fixed operating range. A driving circuit (108) is included for providing a first electrical signal to polarize the ceramic stack (102) and for providing a second electrical signal to generate a mechanical output signal in the ceramic stack (102). Finally, a mechanism (110) is included for transmitting the mechanical output signal from the ceramic stack (102) to a fluid medium. In a preferred embodiment, a PMN-PT ceramic stack (102) is in intimate enclosed contact with an elliptical-shaped outer projector shell (110). The Curie temperature Tm of the PMN-PT is selected to maximize the electrostrictive effects of the ceramic stack (102) for improving projector performance. The stack (102) is surrounded by a heating coil (106) which is controlled by a temperature/heater control mechanism (104) to achieve and maintain the stack operating temperature within a fixed range. The ceramic stack (102) is polarized by a d.c. biasing circuit signal and mechanical vibrations are generated within the stack (102) by an a.c. driving circuit signal. The mechanical vibrations of the ceramic stack (102) cause excursions in the outer projector shell which, in turn, produce acoustic signals in a body of water. First and second alternative embodiments (200, 300) are disclosed with each embodiment housing at least one PMN-PT ceramic stack.