Optimization of a collapsed mode CMUT receiver for maximum off-resonance sensitivity

Date
2018-07-28
Advisor
Supervisor
Co-Advisor
Co-Supervisor
Instructor
Source Title
Journal of Microelectromechanical Systems
Print ISSN
1057-7157
Electronic ISSN
Publisher
Institute of Electrical and Electronics Engineers
Volume
27
Issue
5
Pages
921 - 930
Language
English
Type
Article
Journal Title
Journal ISSN
Volume Title
Series
Abstract

We propose an airborne collapse capacitive micromachined ultrasonic transducer (CMUT) as a practical viable ultrasound transducer capable of providing a stable performance at the off-resonance frequencies. Traditional practice is to bias the CMUT plate close to collapse voltage to achieve high coupling coefficient and sense the incoming ultrasound as an open-circuit receive voltage signal of the transducer or short-circuit receive current (SCRC). Maintaining CMUT plate in the vicinity of collapse threshold is rather difficult. In this paper, an analytic approach to design an airborne collapsed-mode CMUT for maximum off-resonance sensitivity is presented. We use small-signal circuit model to evaluate the performance of a collapsed CMUT for varying operating conditions. CMUT operational parameters that yield the highest off-resonance SCRC are directly obtained from performance design curves. Collapsed CMUT plate is then biased in a critical biasing region that produces a stable and maximum off-resonance sensitivity. We experimentally verify and measure a stable sensitivity of a fabricated collapsed CMUT cell of -60 dB V/Pa at 100 kHz when biased between 50 to 65 V. We characterize our linear circuit model performance against the measured performance of collapsed CMUT in air within 4-dB tolerance. [2018-0058]

Course
Other identifiers
Book Title
Keywords
CMUT, Collapsed CMUT sensitivity, Critical biasing region, Off-resonance, Small-signal circuit model
Citation
Published Version (Please cite this version)