Patent ID: 6420816
Filing Date: 2002-07-16
Classification: G10K,H03H

Abstract:
A method for exciting Lamb waves in a plate using an IDT (interdigital transducer) having a layer of piezoelectric material on one of whose surfaces two electrodes are mounted which engage in one another like fingers, the IDT being coupled acoustically to the plate by the other of the surfaces of the layer, the method comprising the steps of:applying a radio-frequency AC voltage to the electrodes causing cyclically occurring material compressions and rarefactions, a so-called thickness vibration, in the piezoelectric layer between the electrode fingers resulting in the propagation of longitudinal waves; matching the speed of propagation or speed of sound of the longitudinal waves with the phase velocity with which an s0 mode Lamb wave propagates in the material of the plate; and selecting the distance between fingers of the electrodes such that it is equal to half the wavelength &lgr;/2 of the longitudinal wave initiated in the piezoelectric layer.