Electrical control of the elastic wave propagation in a piezoelectric plate: reduction of the crosstalk in a multi- element ultrasonic transducer
Résumé
The cross couplings in a multi-element ultrasonic transducer create perturbations in its radiation, affecting image quality. The crosstalk phenomenon increases the number of vibrating elements by comparison to the number of electrically excited elements and produces spurious guided modes. Solutions have been proposed to reduce the crosstalk, for example, the passive mechanical decoupling between the elements, i.e. varying the depth of the periodic cut of the piezoelectric ceramics and also an active electrical decoupling [1], in applying to the other elements, except to the active one, a suitable electric voltage. This work proposes another possibility by using a passive electrical decoupling. A homogeneous piezoelectric plate, covered on one side by a 1D periodic arrangement of thin metallic electrodes and on the other side by a full metallic electrode, is considered. Through electrical boundary conditions applied to the electrodes, band gap location and width of guided elastic waves can be tuned to a range including the resonance frequency of the first piezoelectric thickness mode. Finite element analysis and experimental measurements show the appearance of band gaps in the dispersion curves, which limits the inter-element couplings and thus the parasitic signals in the radiation. Bibliography: [1] BYBI, A., et al. Electrical method for crosstalk cancellation in transducer arrays. NDT & E International, 2014, vol. 62, p. 115-121.
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