Accurate Radiation Impedance Analysis for CMUT Design

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Abstract

The transducer resonance frequency is a key parameter for the field of ultrasound. The resonance frequency in vacuum is well understood, and an analytical expression for the center frequency in immersion was derived by Lamb in 1920 [1], however this expression has limited validity. Importantly, the model fails to cover plate aspect ratios needed by imaging requirements and met by recently fabricated medical Capacitive Micromachined Ultrasonic Transducers (CMUTs). Based on the equation of motion a new expression for the resonance frequency in immersion is derived. The influence of the immersion medium is included via the radiation impedance, which is approximated using the well-known Taylor expansion, yielding results similar to Lamb's. For precision at smaller aspect ratios, this work proposes using the Padé approximant instead. Comparing the frequency ratio to FEM simulations, the Padé approximant shows a fourfold reduction in error from 12.0% to 3.0%.
Original languageEnglish
Title of host publicationProceedings of 2022 IEEE International Ultrasonics Symposium (IUS)
Number of pages4
PublisherIEEE
Publication date2022
ISBN (Print)978-1-6654-7813-7
ISBN (Electronic)978-1-6654-6657-8
DOIs
Publication statusPublished - 2022
Event2022 IEEE International Ultrasonics Symposium - Venice, Italy
Duration: 10 Oct 202213 Oct 2022

Conference

Conference2022 IEEE International Ultrasonics Symposium
Country/TerritoryItaly
CityVenice
Period10/10/202213/10/2022

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