Broad band, high frequency, high sensitivity beam forming array

Abstract

A sonar array which is operable at a broad range of frequencies, has a high free-field voltage sensitivity and is operable at high hydrostatic pressures. The array includes sensor elements made of a piezoelectric material, a backing plate which supports the sensor elements, a dielectric-elastic insulator positioned between the sensor elements and the backing plate, and backing blocks corresponding, respectively, to the sensor elements, each backing block positioned between a corresponding sensor element and the insulator. The sensor elements are arranged in staves, the staves forming four separate quadrants, the sensor elements in each stave being arranged in parallel and series combinations, so that the sonar array is operable between a frequency range of 10 kHz to above 100 kHz, each stave has a free-field voltage sensitivity of -186 dB re 1V/μPa or greater between the frequency range and the free-field voltage sensitivity does not change more than plus or minus 2 dB at hydrostatic pressures varying from 20 to 4481.6 kPa.

What is claimed is: 
     
       1. An acoustic beam forming array comprised of: means for sensing acoustic waves generated by variations in hydrostatic pressures in a surrounding medium between a frequency range of 10 kHz to 100 kHz and having a free-field voltage sensitivity of at least -186 dB re 1V/μPa; and   means for protecting said sensing means from physical damage having a sound speed and density approximately equal to that of water so that acoustic waves reach said sensing means without being noticeably affected by said protecting means.   
     
     
       2. An array, as in claim 1, wherein said sensing means is a plurality of sensing elements structures. 
     
     
       3. An array, as in claim 2, wherein said each sensing element structures of the plurality of sensing element structures are further comprised of a sensing element, support means and a dielectric-elastic insulator positioned between each sensing element of the plurality of sensing elements and the support means. 
     
     
       4. An array, as in claim 3, wherein the sensing element is a piezoelectric material. 
     
     
       5. An array, as in claim 4, wherein the piezoelectric material is lead titanate. 
     
     
       6. An array, as in claim 3, wherein the dielectric-elastic insulator is buytl rubber. 
     
     
       7. An array, as in claim 3, wherein said support means is further comprised of a plurality of backing blocks corresponding, respectively, to the sensing elements, each backing block positioned between a corresponding sensor element and the insulator. 
     
     
       8. An array, as in claim 7, wherein the backing blocks are metal. 
     
     
       9. An array, as in claim 8, wherein the metal is tungsten. 
     
     
       10. An array, as in claim 3, wherein the sensor elements are arranged in staves, the staves forming four separate quadrants of the array, the sensor elements in each stave being arranged in parallel and series combinations, so that the array operates between a frequency range of 10 kHz to above 100 kHz, each stave having a free-field voltage sensitivity of -186 dB re 1V/μPa or greater between the frequency range. 
     
     
       11. An array, as in claim 10, wherein each quadrant contains ten staves, each stave is divided into columns and rows, with two columns in each stave, each column having a width of one sensor element and each row comprising at least six and no more than 21 sensor elements. 
     
     
       12. An array, as in claim 1, wherein the sensing means is passive. 
     
     
       13. An array, as in claim 1, wherein the sensing means is active. 
     
     
       14. An array, as in claim 1, wherein the sensing means is both active and passive. 
     
     
       15. An array, as in claim 1, wherein the protecting means is comprised of a dome having oil between the dome and the sensing means. 
     
     
       16. An acoustic beam forming array comprised of: a plurality of passive sensing elements capable of sensing variations in hyrostatic pressures between a frequency range of 10 kHz to 100 kHz and having a free-field voltage sensitivity of at least -186 dB re 1V/μPa;   an plurality of insulators corresponding, respectively, to the plurality of sensing elements;   a plurality of backing blocks corresponding, respectively, to the plurality of sensing elements, each backing block positioned between a corresponding sensor element and the insulator; and   said sensing element are arranged in staves, the staves forming four separate quadrants of the array, the sensor elements in each stave being arranged in parallel and series combinations, so that the array operated between a frequency range of 10 kHz to 100 kHz, each stave having a free-field voltage sensitivity of -186 dB re 1V/μPa or greater between the frequency range.   
     
     
       17. An array, as in claim 16, wherein each quadrant contains ten staves, each stave is divided into columns and rows, with two columns in each stave, each column having a width of one sensor element and each row comprising at least six and no more than 21 sensor elements. 
     
     
       18. An acoustic beam forming array comprised of: a plurality of active sensing elements capable of sensing variations in hydrostatic pressures between a frequency range of 10 kHz to 100 kHz and having a free-field voltage sensitivity of at least -186 dB re 1V/μPa;   an plurality of insulators corresponding, respectively, to the plurality of sensing elements;   a plurality of backing blocks corresponding, respectively, to the plurality of sensing elements, each backing block positioned between a corresponding sensor element and the insulator;   said sensing element are arranged in staves, the staves forming four separate quadrants of the array, the sensor elements in each stave being arranged in parallel and series combinations, so that the array operates between a frequency range of 10 kHz to 100 kHz, each stave having a free-field voltage sensitivity of -186 dB re 1V/μPa or greater between the frequency range.   
     
     
       19. An acoustic beam forming array comprised of: a plurality of sensing elements that are both active and passive which are capable of sensing variations in hydrostatic pressures between a frequency range of 10 kHz to 100 kHz and having a free-field voltage sensitivity of at least--186 dB re 1V/μPa;   an plurality of insulators corresponding, respectively, to the plurality of sensing elements;   a plurality of backing blocks corresponding, respectively, to the plurality of sensing elements, each backing block positioned between a corresponding sensor element and the insulator;   said sensing element are arranged in staves, the staves forming four separate quadrants of the array, the sensor elements in each stave being arranged in parallel and series combinations, so that the array operates between a frequency range of 10 kHz to 100 kHz, each stave having a free-field voltage sensitivity of -186 dB re 1V/μPa or greater between the frequency range.