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Cell placement in an element and structural modifications on the array baffle significantly change the bandwidth, band shape and signal to noise ratio of a CMUT receiver array. In this paper, optimum receiver performance tailoring by means of cell placement, cell size variation and use of dummy cells in the array elements is discussed. The performance of the array is modified acoustically at the acoustic...
Large-scale multi-frequency capacitive micromachined ultrasonic transducer (CMUT) arrays consist of thousands of closely packed interlaced large and small membranes for applications such as super-harmonic imaging, multi-band operation, imaging-therapy, contrast and photoacoustic imaging. An accurate nonlinear lumped equivalent circuit model including the effects of the self and mutual acoustic interactions...
In this work, we present a general multi-mode lumped equivalent circuit model for an arbitrary excited circular cMUT cell operated in a small signal regime. It can be considered as a model extension of the modal analysis based equivalent circuit model already presented in [1]. In order to derive this model, a comprehensive description of the radiation impedance by the Bouwkamp's impedance theorem...
We have recently developed a circuit theory based method to analyze large CMUT arrays and shown that mutual acoustic interactions significantly influence the transducer performance. We connect each cell in the array to a radiation impedance matrix that contains the mutual radiation impedance between every pair of cells, in addition to their self radiation impedances. However, efficient analysis of...
We use an accurate nonlinear equivalent circuit model to analyze CMUT arrays with multiple cells, where every cell in the array is coupled to other cells at their acoustic terminals through a mutual radiation impedance matrix. We get results comparable to finite element analysis accuracy. Hence, the analysis of a large array becomes a circuit theory problem and can be scrutinized with circuit simulators...
DC bias voltages are commonly employed in using capacitive micro-ultrasonic transducers (CMUT) for their signal/noise ratio and sensitivity improvements. On the other hand, deformations of CMUT membranes are usually limited by the applied biasing voltages. Bias effects for CMUTs are investigated and modeled in this research, whether the transducers are operating in their transmitting or receiving...
This paper will establish a closed-coupled oscillator model of the wide bandwidth ultrasonic transducer for ultrasound image application. Referring to the acoustical impedance matching theorem, the bandwidth depend on different matching impedance of the matching layers is investigated, and then the wide bandwidth ultrasonic transducer can be obtained. In order to shorten the pulse-echo duration time,...
This paper presents a numerical method for calculating the frequency response of a CMUT with a large number of cells. In a multi-cell configuration, commonly found in CMUTs, each cell is affected by the acoustic loading from neighboring cells. Thus, for an accurate model of a multi-cell CMUT element it is better to consider the mutual acoustic impedance instead of the acoustic impedance of a single...
In this paper, we present an equivalent circuit model for a 2D CMUT array element to asses the overall pulse-echo response. The proposed circuit models the propagation medium, and incorporates reactive effects due to transducer dimensions which are comparable to the acoustic wavelength, and the effects of diffraction and loss. The model has been verified experimentally using hydrophone and pulse-echo...
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