Dense transducer array and method

A transducer array assembly includes a support structure having a plurality of predetermined openings therein for accommodating transducer components. Flexible circuits are embedded in the support structure. Each flexible circuit has first ends being positioned in the support structure predetermined openings. Terminal blocks are joined to the second ends. Transducer elements are positioned in the support structure predetermined openings and placed in electrical communication with the flexible circuit first ends. A polymer material is provided surrounding the transducer elements, said support structure, and said flexible circuit first ends. There is also provided a method for manufacturing the transducer array.

CROSS REFERENCE TO OTHER PATENT APPLICATIONS

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a dense transducer array that provides an acoustic transducer having relatively high operational bandwidth. More particularly, the present invention includes a cable harness component that efficiently provides and organizes numerous conductors within piezocomposite substrates to form transducer arrays with minimum impact on electro-acoustic performance.

(2) Description of the Prior Art

Several underwater sonar applications exist for high frequency wideband transducer arrays having individual elements such as described in U.S. Pat. No. 6,255,761 ('761) and herein incorporated by reference. In order to form and steer acoustic beams with an array of individual elements, the array elements must be spaced not more than one-half the acoustic wavelength at the highest frequency of interest. This implies, for square-shaped elements at least, that the elements' lateral dimensions are inversely proportional to frequency. Therefore, for fully populated radiating apertures, the number of elements increases exponentially as the spacing decreases.

As piezocomposite arrays, such as described in previously mentioned U.S. patent '761, move to higher operational bandwidths and frequencies, the element center to center spacing decreases as the number of elements forming the array aperture increases. The result is a need for a component that organizes the numerous electrical wires found in piezocomposite arrays.

U.S. patent '761 teaches that piezoceramic transducer arrays can be formed from a block of piezoceramic material. A piezoceramic transducer preform can be created by machining away material between preform posts and leaving a base portion of the piezoceramic material on a bottom side of the block and preform posts on a top side of the block. A generalized top surface is defined by the tops of the preform posts opposite from the surface defined by the base. Conductors are inserted in the gaps between the preform posts with the ends of the conductors extending through apertures formed in the base and beyond the general top surface of the preform posts. The combined base, preform post and conductor volume is filled with a liquid polymer which is allowed to harden. Any conductor or polymer extending above the general top surface is removed. The base and conductors extending beyond a selected transducer volume are removed leaving a bottom preform surface. Electrodes are provided on the top preform surface and the bottom preform surface. These electrodes can join with the conductor ends or can be connected to the conductor ends by known methods. This gives a flexible transducer array that can be used for a variety of applications.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a transducer array having densely packed transducer elements.

A second object is providing an array having mechanical isolation between array elements.

It is another object of the present invention to provide a transducer array that handles large numbers of conductors and distributes them in a two-dimensional lattice efficiently in a space-wise fashion.

A further object of the present invention is to provide a transducer array having mechanical isolation between array elements.

Furthermore, it is an object of the present invention to provide a transducer array that supports transmit operation as well as receive operation, while at the same time having cabling that is robust enough to handle high drive signals.

Yet another object is providing a transducer array having a plurality of closely spaced elements capable of transmitting and receiving acoustic signals at high frequencies.

Still another object is providing a method of making a transducer array having closely spaced transducer elements.

Other objects and advantages of the present invention will become more obvious hereinafter with regard to the disclosure contained in the specification and drawings.

Accordingly, there is provided a cable harness component that is particularly suited for transducer arrays. The cable harness component includes a support structure having a plurality of predetermined openings made from a viscoelastic material. A plurality of flexible circuits having conductors communicates between terminal blocks and electrical contacts within the support structure. Terminal blocks are positioned for outside electrical connection.

A cable harness component for a transducer array includes a support structure having a plurality of predetermined openings therein for accommodating transducer components. Flexible circuits are embedded in the support structure. Each flexible circuit has first ends being positioned in the support structure predetermined openings. Terminal blocks are joined to the second ends.

A transducer array assembly includes a support structure having a plurality of predetermined openings therein for accommodating transducer components. Flexible circuits are embedded in the support structure. Each flexible circuit has first ends being positioned in the support structure predetermined openings. Terminal blocks are joined to the second ends. Transducer elements are positioned in the support structure predetermined openings and placed in electrical communication with the flexible circuit first ends. A polymer material is provided surrounding the transducer elements, said support structure, and said flexible circuit first ends. There is also provided a method for manufacturing the transducer array.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly toFIG. 1, there is shown the cable harness component10that includes a plurality of flexible circuits12. Flexible circuits12are embedded within a support structure14and are terminated by conventional connector terminal blocks16. The flexible circuits12have a plurality of flex-circuit ends that can connect the flexible circuits12to electrical contacts on the transducer material that is to be further described hereinafter with reference toFIG. 3. InFIG. 3, two specific flex-circuit ends are identified as12A and12B. The support structure14can be made of any material having the required vibration damping characteristics. Preferably, it is made of a viscoelastic material, known in the art. Support structure14has a plurality of openings14A that will be further described with reference toFIG. 2.

In general, the cable harness component10comprises the support structure14having a plurality of predetermined openings14A and comprised of a viscoelastic material. The plurality of flexible circuits12each have first and second opposite ends with each end having connecting means. The plurality of flexible circuits12are embedded in the support structure14. The plurality of terminal blocks16each have first and second connecting means. The plurality of flexible circuits12and the plurality of terminal blocks16are preferably of an equal number and with the connecting means of the first opposite ends of the flexible circuits being connected to corresponding first connecting means of the terminal blocks16. The second connecting means of the terminal blocks16are preferably made available for connecting to external equipment.

With reference toFIG. 1, it is seen that the cable harness component10has its support structure14, its plurality of flexible circuits12, and its terminal blocks16arranged in an opened three face assembly with the terminal blocks16and support structure14being arranged parallel to and facing each other and are spaced apart by about the horizontal height20of the flexible circuits12.

The flexible circuits12are selected so as to have three sides with the first side having a length22to accommodate mating with the terminal blocks16, the second side of the flexible circuits12has a length24to accommodate mating with the support structure14, and the third side having a length so as to space apart the support structure14and terminal block16and corresponds to about the horizontal height20of the flexible circuits12.

With reference toFIG. 2, it is seen that the cable harness component10is particularly suited to be selected for mating with a transducer array. Transducer array can be formed from a preform18of piezoceramic material. This is more fully described above and in the previously incorporated by reference U.S. Pat. No. 6,255,761 ('761). The preform18comprises a plurality of posts26A,26B . . .26njoined to a base28. In this embodiment, four typical posts,26A,26B,26C and26D, are positioned in a single support structure opening14A to form an array element. Each of the posts26A . . .26nrepresents an electromechanical unit. Openings14A of the support structure14correspond and accommodate the insertion of one or more of the posts. Different embodiments of the invention can incorporate different numbers of posts. The number and lateral spacing of posts can be chosen according to the desired application.

The cable harness component10provides electrical connection for the posts26, as well as electromechanical isolation, so that signals present in one portion of post or group of posts26do not affect another portion of posts26. The interconnection of the cable harness component10to external equipment (not shown) may be accomplished via terminal blocks16which, in turn, are connected to appropriate cabling related to associated external equipment. The interconnection between the cable harness component10and the posts26may be further described with reference toFIG. 3A.

FIG. 3Aillustrates further details of the interconnections between the cable harness component10ofFIG. 1of the present invention and posts26ofFIG. 2. More particularly,FIG. 3Ais an expanded view of a portion of the interconnections between the cable harness component10and posts26for one typical embodiment of the present invention. Further, for the illustration ofFIG. 3A, the flexible circuits12are not shown, but are present under and embedded within the support structure14.

FIG. 3Aillustrates a plurality of connecting means12A and12B. These are the ends of flexible circuit12conductors. InFIG. 3Adirections are indicated by arrows30and32. The flexible circuits12within the support structure14, not shown inFIG. 3A, are arranged so as to run under the support structure14, and are oriented along one direction30with like surfaces running parallel to each other. In direction32perpendicular to direction30, the cable harness/isolator10, in particular to support structure14, does not have any embedded flexible circuits12.

Ends of flexible circuit conductors, identified for one set as connections12A and12B are dimensioned and formed so that connection12A exits out from the associated flexible circuit12upward and out of the associated chamber14A, while connection12B exits out from the associated flexible circuit12downward and out of the associated chamber14A. The12A connection located above the upper surface of the associated posts26is available for positive electrical connection to an associated electrode element, while the12B connection located below the lower surface of the associated posts26is available for negative electrical or ground connection to an associated electrode element.

Cable harness10can be joined to a preform by the following method. Flexible circuits12are positioned within support structure14so that flexible circuit ends, as typically shown at12A, are positioned to extend into an opening14A. The other end of flexible circuit12is joined to an electrical connector16. A ceramic array component, as detailed in U.S. patent '761, is available as a preform18having posts26joined to a base28. Preform18is positioned within support structure14such that four posts26extend into each opening14A. Of course, in other embodiments openings14A can support different numbers of posts. Flexible circuit ends having a first electrical polarity12A are positioned to extend out of each opening14A, and flexible circuit ends having a second electrical polarity12B are positioned to extend proximate the base28of the preform18. In other embodiments, base28can have apertures formed therein for receiving flexible circuit ends12B.

FIG. 3Bshows the next step in creating a transducer array. A settable polymer34is provided around support structure14and within openings14A to retain posts26and flexible circuit ends12A and12B in position within openings14A and base apertures. After the settable polymer hardens, excess polymer34, flexible circuit ends12A and12B and the ceramic array component base28are removed by machining. Upon removal of the polymer and base, a top surface and a bottom surface of the posts26are exposed. On the exposed surface shown inFIG. 3B, circuit end12A is shown among post tops36. Polymer34covers support structure14. The bottom surface looks generally the same as the top surface.

As shown inFIG. 3C, electrodes38can be deposed on the top and bottom surfaces. Post tops36and circuit end12A are shown with hidden lines. Electrode38electrically connects a selected number of post tops36with circuit end12A. In this embodiment four post tops36are joined to a single circuit end12A to form an array element. Electrodes38can be formed by providing a conductive coating on top of circuit ends12A and post surfaces36by any number of methods known in the art. The conductive coating forms an electrode having a first polarity on post surfaces36and an electrode having a second polarity on the bottom of the posts (not shown). These electrodes38can be formed in contact with flexible circuit end such that flexible circuit end having a first electrical polarity is in electrical communication with the electrode having a first polarity on the top of the preform. Likewise, flexible circuit end having a second electrical polarity is in electrical communication with the electrode having a second polarity on the bottom of the post. As shown, multiple posts can be electrically joined by a single electrode to a single flexible circuit end. This process allows thermoforming the ceramic preform18substrate and organizes the numerous conductors making up the large number of array elements, such as the four posts26, forming such an array element.

This can be performed by other methods such as by providing contacts on circuit sheets mounted to the top surface of array and to the bottom surface of array. A polymer coating can be provided outside the electrical components to shield them from the environment.

After the electrodes are formed, the array can be curved forming a finished transducer array40, shown inFIG. 4. This array40includes a plurality of transducer elements indicated by electrode38embedded in a polymeric elastomer34, known in the art. Array40can be prepared for use by covering it with an acoustically transparent coating and providing it on a resilient mounting. Flexible circuits12would likely extend into an interior of a structure.

It should now be appreciated that the practice of the present invention provides a cable harness/isolator10that can be used to form an array of acoustic transducer elements by installing it over a piezoelectric preform18that consists of individual ceramic posts26, backfilling the formed substrate of arrays with polymer, and grinding the upper and lower surfaces of the substrate flat and parallel to each other.

It should be further appreciated that the practice of the present invention allows for handling a relatively large number of conductors entering the terminal blocks16and leaving the flexible circuits12so as to be, in one embodiment, distributed in a two-dimensional lattice efficiently in a space-wise fashion.

Further, it should be appreciated that the practice of the present invention provides mechanical isolation between array elements26deemed critical, by those skilled in the art, for wideband, high frequency grating-lobe free beam steering. The mechanical isolation is provided by the physical spacing between elements26and also the support structure14material.

Further still, it should be appreciated that the mated assembly comprising the cable harness component10and the PZT ceramic preform18supports transmit operation, as well as receive operation, while at the same time those skilled in the art may provide cabling made robust enough to handle high drive signals.

Still further, it should be appreciated that the practice of the present invention by those skilled in the art following the bending and curving principles of U.S. Pat. No. 6,255,761 and applying those principles to the embodiments described with reference toFIGS. 1-4allows electrode substrate to be singly curved for conformal array fabrication.