Speaker
Description
(2) Material and Methods
The fundamental connection between a transducer’s emission and reception sensitivity in the azimuth and elevation angle is its size. Finite elemente simulations showed that approx. half the side length of current generation transducer is required. A circular instead of the current rectangular aperture would result in additional homogenity. Octagon shape transducers are therefore an improvement over previously used rectangular transducers. With the established dice-and-fill technique with 2 additional sawing cuts this form can be achieved. Inspired by compressive sensing, an irregular distribution is applied covering almost the full surface area of US transducer. Further improvements are introduced regarding connectivity and bandwidth.
(4) Discussion and Conclusion
First prototypes were assembled with the described process and first results ares encouraging. Yet, the process is currently not as stable and reliable as aimed for. The curently not fully automatized process lead to variations and in result to the failure of a signifcant portion of the transducer elements. This is currently under intensive investigation with further test prototypes to improve and stabilize the process which promises to lead an improved yield >95%.
(3) Results
Transducer is built up from the backing on which top-side a flexprint is providing the connectivity for the individual transducer elements. Small PZT slabs are glued on copper pads of the flexprint with low temperature curing silver glue. On a matching layer the cured structure is glued also with conductive silver-glue providing the common ground connection, defined distance and parallelity is provided by a laser cutted precise spacer ring. The completed structure is water proofed and mechanical stabilized with a hard-rubber like PU.
Electrical characterization was performancd with a phase-impedance analyzer for all piezo fibres. Ultrasound characteristics were evaluated quantitatively with a hydrophone in a 3-axis water tank.
