Reducing mechanical cross-coupling in phased array transducers using stop band material as backing

J Henneberg,A Gerlach,H Storck,H Cebulla,S Marburg

doi:10.1016/j.jsv.2018.03.021

Abstract

Phased array transducers are widely used for acoustic imaging and surround sensing applications. A major design challenge is the achievement of low mechanical cross-coupling between the single transducer elements. Cross-coupling induces a loss of imaging resolution. In this work, the mechanical cross-coupling between acoustic transducers is investigated for a generic model. The model contains a common backing with two bending elements bonded on top. The dimensions of the backing are small; thus, wave reflections on the backing edges have to be considered. This is different to other researches. The operating frequency in the generic model is set to a low kHz range. Low operating frequencies are typical for surround sensing applications. The influence of the backing on cross-coupling is investigated numerically. In order to reduce mechanical cross-coupling a stop band material is designed. It is shown numerically that a reduction in mechanical cross-coupling can be achieved by using stop band material as backing. The effect is validated with experimental testing.

Highlights

Phased array structures of acoustic transducers are used for acoustic imaging in medical applications and for nondestructive testing
We show that stop band materials can be used to reduce mechanical cross-coupling caused by common backing in phased array structures
A generic model with two single transducers is set up. They are realized as capacitive transducers with bending elements which are bonded on the common backing

Summary

Introduction

Phased array structures of acoustic transducers are used for acoustic imaging in medical applications and for nondestructive testing. Depending on the field of use, the typical operating frequency varies in a range from lower kHz for surround sensing [1,2] up to several MHz for nondestructive testing [3] and medical applications [4]. [5] a quantitative theory for cross-coupling in ultrasonic transducer arrays is presented. Surface waves in the backing and in the load medium in front of the transducers are indicated as reason for cross-coupling. This theory assumes a series of uniformly distributed, unbacked transducer elements.

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Discussion

Conclusion