Influence Of Backing And Matching Layers In Ultrasound Transducers Performance

In this work we have investigated the influence of the backing layer composition and the matching layer thickness in the performance of ultrasound transducers constructed with piezoelectric ceramic discs. We have constructed transducers with backing layers of different compositions, using mixtures of epoxy with alumina powder and/or Tungsten powder and with λ/4 or 3λ/4 thickness epoxy matching layers. The evaluation tests were performed in pulse-echo mode, with a flat target, and in transmission/reception mode, with a calibrated PVDF hydrophone. The acoustical field emitted by each transducer was mapped in order to measure the on-axis and transverse field profiles, the aperture size and the beam spreading. The bandwidths of the transducers were determined in pulse-echo mode. Comparing the evaluation tests results of two transducers constructed with the same backing layer, the one constructed with λ/4 thickness epoxy matching layer showed better performance. The results showed that the transducers constructed with epoxy, alumina and Tungsten powders backing layers have larger bandwidth. The larger depth of field was measured for transducers constructed with epoxy and Tungsten powder backing layers. These transducers and those constructed with epoxy, Tungsten and alumina powders backing layers showed the larger field intensities in the measured transverse profiles.50358696(1999) Standard Guide for Evaluating Characteristics of Ultrasonic Search Units, , ASTM E-1065 1999Desilets, C.S., Fraser, J.D., Kino, G.S., The design of efficient broad-band piezoelectric transducers (1978) IEEE Transactions on Sonics and Ultrasonics, SU-25 (3), pp. 115-125(1996) Ultrasonics Real Time Pulse-echo Systems: Test Procedures to Determine Performance Specification, , IEC-1390(1989) IEEE Guide for Medical Ultrasound Field Parameter Measurements, , IEEE American National Standard Std 790(1978) IEEE Standard on Piezoelectricity, , IEEE American National Standard Std 176Inoue, T., Ohta, M., Takahashi, S., Design of ultrasonic transducers with multiple acoustic matching layers for medical applications (1987) IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 34 (1)Lockwood, G.R., Turnbull, D.H., Foster, F.S., Fabrication of high frequency spherically shaped ceramic transducers (1994) IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 41 (2)Mitra, R., Saksena, T.K., Study on the vibrational characteristics of ultrasonic transducers using tapered piezoelectric ceramic elements (1995) Journal of the Acoustical Society of America, 58 (2)Sayers, C.M., Tait, C.E., Ultrasonic properties of transducer backing (1984) Ultrasonics, 22 (2