VERY-LOW-FREQUENCY HIGH-POWER SONAR PROJECTOR

A VLF HIGH-POWERED BROADBAND SOURCE FOR ACTIVE SURVEILLANCE IS PROPOSED, BASED ON A NOVEL, PROPRIETARY TRANSDUCER ELEMENT: VIZ, A MODIFIED FLEXURE BAR WITH AN ELECTRODYNAMIC DRIVE AND TERMED A FITZ-GERALD FLEXBAR. THE COMBINATION OF THE FLEXBAR PRINCIPLES (INCLUDING TRUE NODAL MOUNTS) TOGETHER WITH A NEW HIGH PERFORMANCE MAGNETIC MATERIALS (E.G., SAMARIUM COBALT AND NEODYMIUM) MEANS THAT ELECTROMECHANICAL COUPLING COEFFICIENTS OF \0.6 CAN PROBABLY BE ACHIEVED. THE FLEXBARS ARE ARRANGED IN A CYLINDRICAL CONFIGURATION, WITH THE CYLINDER INTERIOR ACTING AS A HELMHOLTZ RESONATOR. IT IS SHOWN THAT, WITH THE PROPER SELECTION OF DESIGN PARAMETERS, SOURCE LEVELS OF 190-230 DB RE 1 MICRO PA AT 1 METER CAN PROBABLY BE ACHIEVED OVER THE FREQUENCY RANGE OF 5-40 HZ. TO DEMONSTRATE FEASIBILITY AND ESTABLISH A TECHNOLOGY BASE, IT IS PROPOSED TO FIRST DEVELOP A SMALLER PROJECTOR MODULE, SCALED-UP IN FREQUENCY BY A FACTOR OF 4; I.E., A THREE OCTAVE BAND OF 20-160 HZ. PHASE-I WOULD BE PRIMARILY CONCERNED WITH TRANSDUCER ELEMENT DEVELOPMENT. PHASE-II WOULD BE DIRECTED TOWARD DESIGNING, FABRICATING, AND TESTING A FREQUENCY SCALED (X4) PROJECTOR MODULE. BASED ON THE PERFORMANCE OF THE SCALED MODEL, A FULL-SIZED PROJECTOR MODULE IS PROPOSED TO BE CONSTRUCTED IN PHASE III.