Transmitting CMUT Arrays without a DC Bias (original) (raw)
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Circuit theory based analysis of CMUT arrays with very large number of cells
2013 IEEE International Ultrasonics Symposium (IUS), 2013
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 very large arrays is challenging, which may become computationally cumbersome. To partition the problem, we electrically drive a single element in the array and keep the rest undriven but biased and with their electrical ports terminated with a load. The radiation impedance matrix can be partitioned and rearranged to represent these loads in a reduced form. In this way, only the driven element can be simulated by coupling its cells through this reduced impedance matrix. This method considerably reduces the number of cells and the size of the original radiation impedance matrix at the expense of calculating the inverse of a large complex symmetric matrix.
Circuit theory based modeling and analysis of CMUT arrays
2013
CIRCUIT THEORY BASED MODELING AND ANALYSIS OF CMUT ARRAYS Hüseyin Kağan Oğuz Ph.D. in Electrical and Electronics Engineering Advisor: Prof. Dr. Hayrettin Köymen Co-Advisor: Prof. Dr. Abdullah Atalar December, 2013 Many ultrasonic technology applications require capacitive micromachined ultrasonic transducers (CMUTs) to be used in the form of large arrays to attain better performance in terms of powerful, broadband and beam-formed radiated acoustic signals. To entirely benefit from its important characteristics, it is necessary to use analysis tools that are capable of handling multiple CMUT cells. In this regard, finite element analysis (FEA) tools become unfit for use because in arrays with large number of cells it is computationally very cumbersome and often practically impossible. Although, some simplification had been done by assuming long 1-D CMUT array elements as infinitely long, the results of these FEA simulations are misleading. In these models only a single periodic porti...
Lumped element modeling of CMUT arrays in collapsed mode
2014 IEEE International Ultrasonics Symposium, 2014
This study focuses on modeling collapsed mode operation of CMUT arrays, and obtaining a small signal lumped element model for collapsed mode operation. Having the large signal model for single CMUT from previous studies, the mutual radiation impedance is presented for the collapsed mode, and a large signal model for a CMUT array is obtained for simulating the operation in both uncollapsed and collapsed modes. For faster computation, a small signal model for a CMUT cell is derived by linearizing the collapsed mode operation at a given bias point, and the computation time is reduced significantly. Using this model we are able to simulate a large array of collapsed CMUT cells.
Multirow linear cMUT array using cMUTs and multiplexing electronics
Ultrasonics, IEEE Symposium, 2009
A large area reconfigurable imaging array for research purposes is being developed with co-integrated cMUTs and control electronics. The goal is a 2.5cm 2D tileable module with >16,000 transducer sub-elements spaced at a pitch of 185um in X and Y dimensions. As a prototype demonstration of some of the goals of this effort, a multi-row linear array using cMUTs and external multiplexing electronics was designed and fabricated. In this paper the challenges of trenched cMUT attach to a laminate interposer as part of a tileable module will be discussed. The architecture of the tileable module build-up for manufacturability, reliability, acoustic planarity, and reduced spacing between tiles and cMUT chips will also be addressed. Finally, a first prototype will be shown and experimental acoustic results with the new cMUT-based probe will be presented.
P2P-5 Radiation Impedance and Equivalent Circuit for Immersed CMUT Array Element
… Symposium, 2006. IEEE, 2006
In this paper, we present equivalent circuit for immersed capacitive micromachined ultrasonic transducers (cMUT), based on an accurate parametric model. We also present an accurate approximation for the radiation impedance cMUT. We develop a design approach for immersed cMUTs using the equivalent circuit. We demonstrate that the equivalent circuit predicts the performance of a cMUT array element composed of many cells in parallel. We investigate the applicability of the equivalent circuit in designing cMUT array elements.
A 256-Element Spiral CMUT Array with Integrated Analog Front End and Transmit Beamforming Circuits
2018 IEEE International Ultrasonics Symposium (IUS), 2018
MEMS-based Capacitive Micromachined Ultrasonic Transducer (CMUT) technology enables the development of advanced transducer-electronics integrated multi-chip modules (MCM) for medical imaging applications. In this paper, we present the design, fabrication and characterization of a 256-element CMUT spiral array integrated with a 256-channel analog front end (AFE) ASIC featuring highvoltage unipolar pulsers, low-noise amplifiers and a programmable transmit beamformer. The spiral array, designed to perform volumetric beam steering at 7 MHz, is characterized by a density-tapered layout of 220mumathbfm220\mu\mathbf{m}220mumathbfm -wide hexagonal elements distributed over a quasi-circular area of 10 mm diameter. The CMUT and the AFE were co-designed, fabricated and interconnected through an acoustically optimized 3-D packaging method. The resulting MCM was electromechanically and acoustically characterized, demonstrating the potential of the proposed approach for integrated 2-D CMUT array fabrication.
Assessing the Microfabrication-Related Variability of the Performance of CMUT Arrays
IEEE open journal of ultrasonics, ferroelectrics, and frequency control, 2022
This paper addresses the assessment of the variability of CMUT arrays' electro-mechanical and acoustic performance, as related to the tolerance of the CMUT vertical dimensions due to the microfabrication process. A 3-factors 3-levels factorial sensitivity analysis is carried out to compute the main effects and the interaction effects of the moving plate thickness, the passivation layers thickness, and the sacrificial layer thickness, on the CMUT resonance frequency, collapse voltage, and static capacitance, as well as on the transmission and reception sensitivity amplitude and bandwidth and time delay in watercoupled condition. The analysis is performed by means of FEM simulations of the CMUT static behavior and dynamic response, and the findings are compared to experimental data.
2012 IEEE International Ultrasonics Symposium, 2012
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. We study the mutual acoustic interactions that arise through the immersion medium due to the influence of the generated pressure field by each cell on the others. We compare the performance of different 1D cMUT arrays, where each element is half-wavelength wide and 10 and 20 wavelengths long at the resonance frequency of a single cell.
Acoustical tuning of CMUT receiver arrays
2016 IEEE International Ultrasonics Symposium (IUS), 2016
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 port of the elements.