Lamb wave graphic tablet

A graphic sensor based on the measurement of the propagation time of an acoustic wave train is described. Lamb waves are launched in a plate of ordinary glass by piezoelectric bars bonded to the edges of the plate. They are detected at their arrival under the tip of the drawing pencil by a small piezoelectric disc placed in the pencil body. The useful area of the tablet is 19×27 cm2; the resolution is about 0.2 mm.     

PVF2 tranducers for Rayleigh waves

PVF2 thin-film transducers have been incorporated in a 8 MHz s.a.w. delay line. The flexibility of the transducer material will allow its use on curved as well as plane surfaces. Losses at frequencies typical in n.d.t. applications are in principle relatively low; it is for such tasks that the use of PVF2 s.a.w. transducers is seen as particularly appropriate.     

Acoustic-surface-wave filters

Two examples of filters using Rayleigh waves, at the frequencies of 25 MHz and 150 MHz, are described. The shape, almost rectangular, of the frequency response is determined by drawing one transducer.     

Determination of a nonlinear parameter for acoustic-surface-wave convolution in LiNbO3

A 1-dimensional, single-parameter model is used to calculate the voltage induced by two acoustic surface waves propagating in opposite directions in a nonlinear material. A value of the single parameter for LiNbO3 is found to be K = 8±3 C/m2 from experiment at 150 MHz.     

Continuous deflection of light with longitudinal acoustic waves

With a quartz-crystal acoustic light modulator, 600 spots have been obtained by only varying the frequency of the longitudinal acoustic waves. The center frequency of the acoustic waves was 780 MHz.     

Calculation of the bandshape factor of a piezoelectric thin-film transducer

This analysis examines the mechanical bandwidth of a particular transducer structure and gives a way to deduce the electrical bandwidth of the whole system from the electrical components of the circuit and the mechanical bandwidth. An example is given for a cadmium-sulphide transducer on sapphire with a gold intermediate electrode.     

Pyroelectric imaging of defects in bulk acoustic wave lithium niobate transducers

Initial results on a method for testing piezoelectric transducers made of a polar material are presented. The method consists of measuring the voltage induced across the transducer electrodes by an intensity-modulated laser beam scanning the surface. Applied to a bulk acoustic wave LiNbO3 transducer, this technique has revealed domains with Z-axis reversed.     

Beryllium 100 ns acoustic delay line

A beryllium single crystal is used to fabricate an acoustic delay line. The sputtered ZnO transducers are deposited on the (0001) surfaces. A delay of 110 ns is obtained in the range 1000?2000 MHz with an insertion loss of about 50 dB and spurious responses below 70 dB.