Browsing by Author "Ozgurluk, A."

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Open Access
An improved lumped element nonlinear circuit model for a circular CMUT cell
(IEEE, 2012) Köymen, Hayrettin; Atalar, Abdullah; Aydogdu, E.; Kocabas, C.; Oguz, H. K.; Olcum, S.; Ozgurluk, A.; Unlugedik, A.
This paper describes a correction and an extension in the previously published large signal equivalent circuit model for a circular capacitive micromachined ultrasonic transducer (CMUT) cell. The force model is rederived so that the energy and power is preserved in the equivalent circuit model. The model is able to predict the entire behavior of CMUT until the membrane touches the substrate. Many intrinsic properties of the CMUT cell, such as the collapse condition, collapse voltage, the voltage-displacement interrelation and the force equilibrium before and after collapse voltage in the presence of external static force, are obtained as a direct consequence of the model. The small signal equivalent circuit for any bias condition is obtained from the large signal model. The model can be implemented in circuit simulation tools and model predictions are in excellent agreement with finite element method simulations.
Open Access
Lumped element model of single CMUT in collapsed mode
(IEEE, 2013) Aydoğdu, Elif; Ozgurluk, A.; Oguz H.K.; Atalar, Abdullah; Köymen, Hayrettin
In this study, an equivalent electrical circuit model for a single circular CMUT in both uncollapsed and collapsed modes is obtained. In order to model the collapsed mode mechanics, the governing differential equation is solved semi-analytically for a large number of normalized cases. Then the calculations are adapted to the equivalent electrical circuit model. The model uses the self radiation impedance of both uncollapsed and collapsed modes. The model is fully parametric in such a way that a CMUT cell of given dimensions and parameters can be simulated under an arbitrary large signal excitation. Transient simulations can be performed in less than a minute with a circuit simulator. Transient and frequency domain simulations are consistent with finite element analysis results. © 2013 IEEE.
Open Access
Parametric nonlinear lumped element model for circular CMUTs in collapsed mode
(2014) Aydoǧdu, E.; Ozgurluk, A.; Atalar, Abdullah; Köymen, Hayrettin
We present a parametric equivalent circuit model for a circular CMUT in collapsed mode. First, we calculate the collapsed membrane deflection, utilizing the exact electrical force distribution in the analytical formulation of membrane deflection. Then we develop a lumped element model of collapsed membrane operation. The radiation impedance for collapsed mode is also included in the model. The model is merged with the uncollapsed mode model to obtain a simulation tool that handles all CMUT behavior, in transmit or receive. Large- and small-signal operation of a single CMUT can be fully simulated for any excitation regime. The results are in good agreement with FEM simulations. © 2014 IEEE.
Open Access
Radiation impedance of collapsed capacitive micromachined ultrasonic transducers
(Institute of Electrical and Electronics Engineers, 2012) Ozgurluk, A.; Atalar, Abdullah; Köymen, Hayrettin; Olçum, S.
The radiation impedance of a capacitive micromachined ultrasonic transducer (CMUT) array is a critical parameter to achieve high performance. In this paper, we present a calculation of the radiation impedance of collapsed, clamped, circular CMUTs both analytically and using finite element method (FEM) simulations. First, we model the radiation impedance of a single collapsed CMUT cell analytically by expressing its velocity profile as a linear combination of special functions for which the generated pressures are known. For an array of collapsed CMUT cells, the mutual impedance between the cells is also taken into account. The radiation impedances for arrays of 7, 19, 37, and 61 circular collapsed CMUT cells for different contact radii are calculated both analytically and by FEM simulations. The radiation resistance of an array reaches a plateau and maintains this level for a wide frequency range. The variation of radiation reactance with respect to frequency indicates an inductance-like behavior in the same frequency range. We find that the peak radiation resistance value is reached at higher kd values in the collapsed case as compared with the uncollapsed case, where k is the wavenumber and d is the center-to-center distance between two neighboring CMUT cells.