Silicon Micromachined Ultrasonic Transducers

Abstract-Capacitive micromachined ultrasonic transducers (cMUT) have large bandwidths, but they typically have low conversion efficiencies. This paper defines a performance measure in the form of a gain-bandwidth product and investigates the conditions in which this performance measure is maximized. A Mason model corrected with finite-element simulations is used for the purpose of optimizing parameters. There are different performance measures for transducers operating in transmit, receive, or pulse-echo modes. Basic parameters of the transducer are optimized for those operating modes. Optimized values for a cMUT with silicon nitride membrane and immersed in water are given. The effect of including an electrical matching network is considered. In particular, the effect of a shunt inductor in the gain-bandwidth product is investigated. Design tools are introduced, which are used to determine optimal dimensions of cMUTs with the specified frequency or gain response.

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“…2 [18]. In this model, the left-hand side of the transformer is electrical, and the right-hand side is mechanical.…”

Section: Mason Model Corrected By Finite-element Methods Simulationsmentioning

confidence: 99%

Optimization of the gain-bandwidth product of capacitive micromachined ultrasonic transducers

Ölçüm

Senlik

Atalar

2005

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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“…A pair of electrostatic devices, consisting of polished convex metal backplates with a 10 mm radius of curvature and 5 lm thick metallised PET dielectric film, was employed for both generation and detection of ultrasound. These devices operated at a frequency of 400 kHz with a À6 dB bandwidth of 300 kHz, and their basic operation has been detailed elsewhere [6][7][8][9].…”

Section: Methodsmentioning

confidence: 99%

“…Transducers based on an electrostatic or capacitance principle have generated much recent interest due to their ability to efficiently generate and detect broadband ultrasound in air at MHz frequencies, and there is a considerable body of research into the fabrication, characterisation and modelling of such devices (e.g. [6][7][8][9]). In previous work by Wright et al [10], ultrasonic tomographic reconstruction of temperature and flow fields was achieved in air using air-coupled capacitance transducers and a parallel-beam geometry.…”

Section: Introductionmentioning

confidence: 99%

Ultrasonic imaging in air using fan-beam tomography and electrostatic transducers

Ingleby

Wright

2002

Ultrasonics

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Air-coupled ultrasonic capacitance transducers operating at frequencies of up to 1 MHz have been employed in a fan-beam configuration for the cross-sectional tomographic imaging of temperature fields and flow fields in air, and the location of solid objects. Separate transmitter and receiver transducers were manufactured using thin polymer dielectric membranes and polished metal backplates, and used to acquire through-transmission data. The fan-beam reconstruction was developed in LabVIEW â using a re-bin routine combined with a filtered backprojection algorithm and a difference technique to generate the cross-sectional images. The system was first used to reconstruct images showing the locations of solid objects positioned within the scanned region through interpretation of the arrival time of the transmitted ultrasound. The technique was then extended to image the temperature fields produced in air above a small heat source and the flow field produced by a nozzle connected to a regulated compressed air source. Reconstructed temperatures were within 4% of the measured background air temperature and 9% of the air temperature measured above the heat source. Reconstructed images of the flow field above a small nozzle were also presented, showing that the horizontal component of the flow velocity could be resolved using this method. Ó

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“…A transducer more suitable for generating and receiving ultrasound in gases is based on an electrostatic principle [11][12][13][14][15], and is shown schematically in Fig. 1.…”

Section: Introductionmentioning

confidence: 99%

“…This type of device is extremely sensitive, demonstrates good bandwidth characteristics due to its nonresonant nature, and can generate and detect ultrasound in gases at frequencies in excess of 1 MHz [12]. The membrane thickness, bias voltage and the surface properties of the back plate influence the beam profile, frequency response and sensitivity of the transducer [11][12][13][14][15]. The use of electrostatic transducers in gas flowmetry has received little attention to date although previous work has investigated their use in tomographic reconstruction of flow fields in gases [16].…”

Section: Introductionmentioning

confidence: 99%

Ultrasonic measurement of gas flow using electrostatic transducers

O’Sullivan

Wright

2002

Ultrasonics

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Ultrasonic gas flowmeters typically use narrowband piezoelectric transducer arrangements for interrogating the flow of gas in a pipe. In this work, the suitability of broadband electrostatic transducers operating at frequencies of up to 1 MHz for ultrasonic measurement of gas flow has been investigated. The transit time method of ultrasonic gas flow measurement was adopted and experiments were carried out using a laboratory test rig capable of producing a range of gas flowrates up to 17.5 m/s. The test rig also allowed easy interchange of different prototype flowmetering sections. Times of flight of ultrasonic waves interrogating the gas flow were measured using separate send/receive electrostatic transducer arrangements. Two flowmeter configurations were considered. The first interrogated the flow at 45°in contra-propagating upstream and downstream directions. The second consisted of an upstream interrogation at 45°to the gas flow and an interrogation made normal to the flow direction. k factors correlating the fluid velocity along the ultrasonic path with the mean fluid velocity in the pipe were calculated using experimental ultrasonic data and anemometer measurements. All transducer configurations were numerically modelled using the computational fluid dynamics software package FLOTRAN Ó (ANSYS Inc.). Theoretical gas flow velocities for both transducer arrangements were subsequently compared with experimental values and found to be in excellent agreement. A flow-dependent frequency shift of the received ultrasonic signals was also observed simultaneously with the transit time measurement. Ó

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Silicon Micromachined Ultrasonic Transducers

Cited by 63 publications

References 3 publications

Optimization of the gain-bandwidth product of capacitive micromachined ultrasonic transducers

Optimization of the gain-bandwidth product of capacitive micromachined ultrasonic transducers

Ultrasonic imaging in air using fan-beam tomography and electrostatic transducers

Ultrasonic measurement of gas flow using electrostatic transducers

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