Home // International Journal On Advances in Systems and Measurements, volume 15, numbers 1 and 2, 2022 // View article
Authors:
Thasnim Mohammed
Sazzadur Chowdhury
Keywords: CMUT; electrostatic spring softening; fluid loading effect; resonant frequency drift; FFT-based microelectronic compensation.
Abstract:
This paper presents a Fast Fourier transform (FFT) based bias voltage control scheme to compensate for the resonant frequency drift of Capacitive Micromachined Ultrasonic Transducers (CMUTs) due to fluid loading. A unified mathematical model for the resonant frequency of a CMUT that includes the electrostatic spring softening effect and the fluid loading effect due to the coupled fluidic layer has been developed that provides the basis of the proposed approach. The actual resonant frequency drift has been obtained by comparing the center frequencies of transmitted and received signals extracted through analog-to-digital conversion (ADC) and subsequent FFT of both signals. The frequency drift is then compensated by dynamically adjusting the DC bias voltage that modifies the electrostatic spring softening parameter. Analytical and COMSOL based 3D Finite Element Analysis (FEA) results show that the drift in the resonant frequency of a 6 MHz CMUT operated in water can be compensated by adjusting the bias voltage by 2% from its 75% pull-in voltage value to render an improvement of 4% in lateral and axial resolutions in imaging applications. A bias voltage adjustment of 9% of the 75% pull-in voltage value is necessary to achieve an improvement of 20.74% when the CMUT is operated in glycerol. The scheme can be realized using standard commercially available microelectronic components to improve the accuracy and reliability of diagnostic imaging and non-destructive evaluation (NDE).
Pages: 38 to 47
Copyright: Copyright (c) to authors, 2022. Used with permission.
Publication date: June 30, 2022
Published in: journal
ISSN: 1942-261x