CMUT array modeling through free acoustic CMUT modes and analysis of the fluid CMUT interface through Fourier transform methods

A method for analyzing capacitive micromachined ultrasonic transducer (CMUT) arrays and arrays of elements composed of several CMUTs is proposed. It is based on a combination of a free acoustic mode description of an isolated CMUT, and the coupling of these modes to the fluid in which waves should be excited or detected through an impedance matrix that will depend on frequency. The parameters of the model describing the isolated CMUT is independent of frequency and excitation of neighbor CMUTs, whereas the acoustic impedance matrix describing the coupling to the fluid will depend on both the excitation of neighbor CMUTs and frequency. Hence, this splitting of the calculations has a potential for saving computer time. The analysis gives transfer functions from excitations that vary harmonically with time and space along the array surface to CMUT parameters as current, mode excitations, or output acoustic pressure. Based on this, the response of essentially arbitrary excitations of the CMUTs may be obtained. The method is used to analyze an infinitely large array of circular CMUTs on a rectangular grid. The CMUTs are assumed to be operating in collapsed mode. Sharp resonances are shown to occur that could be significantly damped by adding series resistors to the CMUTs or increasing the water viscosity.

[1]  B. Khuri-Yakub,et al.  Surface micromachined capacitive ultrasonic transducers , 1998, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[2]  O. Oralkan,et al.  Simulation and experimental characterization of a 2-D capacitive micromachined ultrasonic transducer array element , 1999, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[3]  O. Oralkan,et al.  Capacitive micromachined ultrasonic transducer arrays for medical imaging: experimental results , 2001, 2001 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.01CH37263).

[4]  G.G. Yaralioglu,et al.  An implementation of a microfluidic mixer and switch using micromachined acoustic transducers , 2003, The Sixteenth Annual International Conference on Micro Electro Mechanical Systems, 2003. MEMS-03 Kyoto. IEEE.

[5]  Edward Hæggström,et al.  Fabricating capacitive micromachined ultrasonic transducers with wafer-bonding technology , 2003 .

[6]  O. Oralkan,et al.  Volumetric ultrasound imaging using 2-D CMUT arrays , 2003, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[7]  B. Khuri-Yakub,et al.  Characterization of one-dimensional capacitive micromachined ultrasonic immersion transducer arrays , 2001, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[8]  W. Benecke,et al.  Derivation of a 1D CMUT model from FEM results for linear and nonlinear equivalent circuit simulation , 2003, IEEE Symposium on Ultrasonics, 2003.

[9]  Lawrence E. Kinsler,et al.  Fundamentals of acoustics , 1950 .

[10]  A. Ronnekleiv.  Noise and element impedance in ultrasonic arrays with small elements , 2001, 2001 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.01CH37263).

[11]  Sylvain Ballandras,et al.  Simulation of cMUT radiating in water using a mixed finite element/boundary element approach , 2002, 2002 IEEE Ultrasonics Symposium, 2002. Proceedings..

[12]  H. Skeie,et al.  Acoustic surface waves in piezoelectric materials with periodic metal strips on the surface , 1973 .

[13]  B.T. Khuri-Yakub,et al.  Capacitive micromachined ultrasonic Lamb wave transducers using rectangular membranes , 2003, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[14]  B.T. Khuri-Yakub,et al.  Calculation and measurement of electromechanical coupling coefficient of capacitive micromachined ultrasonic transducers , 2003, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[15]  L. Segel,et al.  Mathematics Applied to Continuum Mechanics , 1977 .

[16]  D. Hutchins,et al.  Cost-effective and manufacturable route to the fabrication of high-density 2D micromachined ultrasonic transducer arrays and (CMOS) signal conditioning electronics on the same silicon substrate , 2001, 2001 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.01CH37263).

[17]  W. Benecke,et al.  Fabrication and characterization of a new capacitive micromachined ultrasonic transducer (cMUT) using polysilicon as membrane and sacrificial layer material , 2003, IEEE Symposium on Ultrasonics, 2003.

[18]  B. Khuri-Yakub,et al.  Capacitive micromachined ultrasonic transducers: next-generation arrays for acoustic imaging? , 2002, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[19]  Tatsuya Omori,et al.  ANALYSIS OF SAW EXCITATION AND PROPAGATION UNDER PERIODIC METALLIC GRATING STRUCTURES , 2000 .

[20]  Reinhard Lerch,et al.  Micromachined transducer design for minimized generation of surface waves , 1999, 1999 IEEE Ultrasonics Symposium. Proceedings. International Symposium (Cat. No.99CH37027).

[21]  B. Bayram,et al.  Collapsed regime operation of capacitive micromachined ultrasonic transducers based on wafer-bonding technique , 2003, IEEE Symposium on Ultrasonics, 2003.

[22]  A. Schroder,et al.  A capacitance ultrasonic transducer for high-temperature applications , 2004, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[23]  I. Ladabaum,et al.  Theory and analysis of electrode size optimization for capacitive microfabricated ultrasonic transducers , 1999, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[24]  B.T. Khuri-Yakub,et al.  Finite element analysis of underwater capacitor micromachined ultrasonic transducers , 2002, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[25]  B.T. Khuri-Yakub,et al.  A new regime for operating capacitive micromachined ultrasonic transducers , 2003, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[26]  Butrus T. Khuri-Yakub,et al.  Fabrication and characterization of surface micromachined capacitive ultrasonic immersion transducers , 1999 .

[27]  Xuecheng Jin,et al.  An efficient electrical addressing method using through-wafer vias for two-dimensional ultrasonic arrays , 2000, 2000 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.00CH37121).

[28]  B. Bayram,et al.  Influence of the electrode size and location on the performance of a CMUT [US transducer] , 2001, 2001 IEEE Ultrasonics Symposium. Proceedings. An International Symposium (Cat. No.01CH37263).

[29]  Butrus T. Khuri-Yakub,et al.  Capacitive micromachined ultrasonic transducers for robotic sensing applications , 2003, Proceedings 2003 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2003) (Cat. No.03CH37453).

[30]  O. Oralkan,et al.  Forward-viewing CMUT arrays for medical imaging , 2004, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[31]  Christofer Hierold,et al.  Surface micromachined ultrasound transducers in CMOS technology , 1996, 1996 IEEE Ultrasonics Symposium. Proceedings.

[32]  I. Ladabaum,et al.  Air coupled through transmission of aluminum and other recent results using MUTs , 1997, 1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118).

[33]  I. Ladabaum,et al.  An improved circuit model of MUTs , 1997, 1997 IEEE Ultrasonics Symposium Proceedings. An International Symposium (Cat. No.97CH36118).