Multiple frequency band acoustic transducer arrays

Abstract

A structure of an acoustic transducer array probe for transmission of acoustic waves from a front radiation surface into an acoustic load material, where said acoustic waves can have frequencies in a high frequency (HF) band and further lower frequency (LF, . . . , LFn, . . . , LFN) bands with N≥1, arranged in order of decreasing center frequency. The acoustic waves are transmitted from separate high and lower frequency arrays stacked together with matching layers in a thickness dimension into a layered structure, with at least a common radiation surface for said high and lower frequency bands. At least for said common radiation surface at least one lower frequency LFn electro-acoustic structure (n=1, . . . , N) comprises a piezoelectric array with an acoustic isolation section to its front face. The acoustic isolation section includes to the front a section composed of a sequence of L≥3 matching layers with interchanging low and high characteristic impedances, where the front layer of said section is one of i) a lower characteristic impedance layer, and ii) a higher characteristic impedance layer, and where at least one lower characteristic impedance layer is made of a homogeneous material.