Optimizing CMUT geometry for high power
Date
2010Source Title
2010 IEEE International Ultrasonics Symposium
Print ISSN
1051-0117
Publisher
IEEE
Pages
2247 - 2250
Language
English
Type
Conference PaperItem Usage Stats
155
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111
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Abstract
Capacitive micromachined ultrasonic transducers (CMUTs) have demonstratedvarious advantages over piezoelectric transducers. However, current CMUT designsproduce low output pressures with high harmonic distortions. Optimizing thetransducer parameters requires an iterative solution and is too time consumingusing finite element (FEM) modelling tools. In this work, we present a method ofdesigning high output pressure CMUTs with relatively low distortion. We analyzethe behavior of a membrane under high voltage continuous wave operation using anonlinear electrical circuit model. The radiation impedance of an array ofCMUTs is accurately represented using an RLC circuit in the model. The maximummembrane swing without collapse is targeted in the transmit mode. Using SPICEsimulation of the parametric circuit model, we design the CMUT cell withoptimized parameters such as the membrane radius (a), thickness (tm),insulator thickness (ti) and gap height (tg). The modelalso predicts the amount of second harmonic at the output. To verify theaccuracy of the results, we built a FEM model with the same CMUT parameters. Thedesign starts by choosing ti for the given input voltage level.First, a is selected for the maximum radiation resistance of the array at theoperating frequency. Second, tm is found for the resonance at theinput frequency. Third, tg is chosen for the maximum membrane swing.Under this condition, a frequency shift in the resonant frequency occurs. Secondand third steps are repeated until convergence. This method results in a CMUTarray with a high output power and with low distortion. © 2010 IEEE.
Keywords
Capacitive micromachined ultrasonic transducerCircuit models
Continuous wave operation
Electrical circuit models
FEM models
Finite elements
Frequency shift
Gap height
High output
High output power
High voltage
High-power
Input voltages
Insulator thickness
Iterative solutions
Low distortion
Modelling tools
Radiation impedance
Radiation resistance
RLC circuit
Second harmonics
Transmit-mode
Circuit theory
Natural frequencies
Optimization
Transducers
Ultrasonics
Ultrasonic transducers