Rayleigh-bloch waves in CMUT arrays
Date
2014Source Title
IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Print ISSN
0885-3010
Publisher
Institute of Electrical and Electronics Engineers Inc.
Volume
61
Issue
12
Pages
2139 - 2148
Language
English
Type
ArticleItem Usage Stats
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Abstract
Using the small-signal electrical equivalent circuit of a capacitive micromachined ultrasonic transducer (CMUT) cell, along with the self and mutual radiation impedances of such cells, we present a computationally efficient method to predict the frequency response of a large CMUT element or array. The simulations show spurious resonances, which may degrade the performance of the array. We show that these unwanted resonances are due to dispersive Rayleigh-Bloch waves excited on the CMUT surface-liquid interface. We derive the dispersion relation of these waves for the purpose of predicting the resonance frequencies. The waves form standing waves at frequencies where the reflections from the edges of the element or the array result in a Fabry-Pérot resonator. High-order resonances are eliminated by a small loss in the individual cells, but low-order resonances remain even in the presence of significant loss. These resonances are reduced to tolerable levels when CMUT cells are built from larger and thicker lates at the expense of reduced bandwidth. © 2014 IEEE.
Keywords
CellsCytology
Dispersions
Frequency response
Resonance
Ultrasonic transducers
Capacitive micromachined ultrasonic transducer
Computationally efficient
Dispersion relations
Electrical equivalent circuit
High-order resonances
Radiation impedance
Resonance frequencies
Surface-liquid interfaces
Dispersion (waves)