ABSTRACTA general set of modeling equations for lossless one-dimensional multilayerultrasound transducers is presented based on first principles. Inparticular, a direct relationship between ultrasound transducer results andthe underlying physical principles of electroacoustics is given. As such,the model may provide better physical understanding for designers not fullyversed in electrical circuits theory or in linear system analyses. The modelis suitable for time-domain analysis and monofrequency design. Specialattention is given to the determination of the time-dependent voltage acrossthe receiver electrodes subject to a general voltage input, but informationon any (dynamic) variable of interest is provided. The basic equationsgoverning the dynamics of the multilayer structure acting as transmitter aswell as receiver are solved by Fourier analysis and by imposing continuityof velocity and pressure between layers. Sound transmission between the twopiezoelectric circuits is assumed to take place in a water bath such thatthe Rayleigh equation can be used to obtain the incoming pressure at thereceiver aperture from the acceleration of the opposing transmitteraperture. Comparison with experimental results is possible by allowingcoupling to external electric impedances. A numerical test case using amultilayered 1-MHz transducer for flow meter applications was considered andgood agreement with experiments was obtained in terms of voltage signals.The transducer contains a half-wavelength stainless steel layer needed toresist corrosion, the ability to operate at temperatures in a wide rangefrom 20 to 150° Celsius, resistance to impact from flowing particlesin the medium, high pressure or vacuum, and pH values up to 10 in somelocations. The influence of epoxy glue and grease acoustic coupling layers--- between the piezoceramics and the stainless steel layer - in the rangefrom 1 to 70 μm was examined. It was shown that, for the same layerthickness, epoxy glue is preferred as compared with grease, both in terms ofsignal shapes and amplitudes. Finally, inclusion of appropriate electricimpedances in the transmitter and receiver circuits is found to affectsignal pulses strongly.
1999 IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control Vol. 46, pp. 1164-1174, 1999
© 1999, by The Institute of Electrical and Electronics Engineers, Inc. All rights reserved.