Browsing by Subject "Transducer"

Now showing 1 - 9 of 9

Open Access
Bilateral CMUT cells and arrays: equivalent circuits, diffraction constants, and substrate impedance
(Institute of Electrical and Electronics Engineers Inc., 2017) Köymen, Hayrettin; Atalar, Abdullah; Taşdelen, A. S.
We introduce the large-signal and small-signal equivalent circuit models for a capacitive micromachined ultrasonic transducer (CMUT) cell, which has radiating plates on both sides. We present the diffraction coefficient of baffled and unbaffled CMUT cells. We show that the substrate can be modeled as a very thick radiating plate on one side, which can be readily incorporated in the introduced model. In the limiting case, the reactance of this backing impedance is entirely compliant for substrate materials with a Poisson's ratio less than 1/3. We assess the dependence of the radiation performance of the front plate on the thickness of the back plate by simulating an array of bilateral CMUT cells. We find that the small-signal linear model is sufficiently accurate for large-signal excitation, for the purpose of the determining the fundamental component. To determine harmonic distortion, the large-signal model must be used with harmonic balance analysis. Rayleigh-Bloch waves are excited at the front and back surfaces similar to conventional CMUT arrays.
Open Access
Design of a wideband and bi-directional transducer for underwater communications
(2007) Elmaslı, Işıl Ceren
A two ceramic layer stacked transducer structure for short range underwater communications at high frequencies is studied in this work. The structure has a wide bandwidth of one octave and operates at 350 kHz center frequency. Transducer structure inherently has two electrical and two acoustic ports. Ceramic layers are matched to water load through quarter wavelength thick matching layers on each radiating face. Using electrical ports separately to compensate for the large acoustic length of the structure in water is also investigated. It is shown that the wide bandwidth operation can be maintained. The beamwidth of the structure is narrow due to end - fire effect of two back – to – back radiating elements.
Open Access
Developing a transducer based on localized surface plasmon resonance (LSPR) of gold nanostructures for nanobiosensor applications
(Trans Tech Publications, 2013) Turhan, Adil Burak; Ataman, D.; Çakmakyapan, S.; Mutlu, M.; Özbay, Ekmel; Vlachos, D. S.; Hristoforou, E.
In this work, we report the nanofabrication, optical characterization, and electromagnetic modeling of various nanostructure arrays for localized surface plasmon resonance (LSPR) based biosensing studies. Comparison of the experimental results and simulation outputs of various nanostructure arrays was made and a good correspondence was achieved.
Open Access
Mutual impedance considerations in two dimensional planar acoustic arrays with square piston elements
(2015-12) Saçma, Mustafa Oğuzhan
Large acoustic arrays have tremendous value in military and civil applications for producing well-formed beams. In order to realize the potential gains of these applications enabled by large acoustic arrays, it is essential to calculate and take into account the acoustic coupling of the sonar arrays. Although many studies have been conducted on this phenomenon, the practical and theoretical studies in public literature remain inadequate especially on mutual radiation impedance of the acoustic sonar arrays. In order to address this need, self and mutual radiation impedances of square piston elements in two-dimensional planar acoustic arrays are investigated in this thesis. Impedance matrices are formed from the self and mutual radiation impedances of these elements. Operation of arrays and possible mutual radiation impedances are analyzed through the active simulations of planar arrays. Importantly, the mutual impedance data is tested on a generic equivalent circuit model of a piston transducer. Resonance of these transducers and Rayleigh-Bloch waves are also observed as the outcome of these tests.
Open Access
Nanofabrication and plasma polymerization assisted surface modification of a transducer based on localized surface plasmon resonance of gold nanostructure arrays for biosensor applications
(S P I E - International Society for Optical Engineering, 2012-07-31) Turhan, A. B.; Ataman, D.; Sen, Y.; Mutlu, M.; Özbay, Ekmel
The nanofabrication and surface modification of a transducer based on localized surface plasmon resonance (LSPR) of gold nanostructure arrays for biosensing was studied. We used electron beam lithography for the nanopatterning technique, which let us choose LSPR sensor properties by providing immense control over nanostructural geometry. A critical step in the utilization of this transducer is to form a selective biolayer over the gold nanostructures. We applied plasma polymerization and wet chemistry techniques for ethylenediamine (EDA) modification and glutaraldehyde immobilization as intermediate layers, respectively. The gold nanostructure arrays were primarily modified using EDA in order to activate the surface with amine groups that are cross-linked with later added avidin molecules by the help of glutaraldhyde layer residing in between. The success of plasma polymerization was validated with x-ray photoelectron spectroscopy measurements. As a last step, we introduced biotin to the surface (biotin has a high affinity for avidin). We were able to detect the LSPR resonance wavelength shift in the transmission spectra at each step of modification, including the avidin-biotin interaction, which acts as a model for specific molecule detection using LSPR. (C) 2012 Society of Photo-Optical Instrumentation Engineers (SPIE).
Open Access
Nanomechanical motion transducers for miniaturized mechanical systems
(MDPI AG, 2017) Kouh, T.; Hanay, M. S.; Ekinci, K. L.
Reliable operation of a miniaturized mechanical system requires that nanomechanical motion be transduced into electrical signals (and vice versa) with high fidelity and in a robust manner. Progress in transducer technologies is expected to impact numerous emerging and future applications of micro- and, especially, nanoelectromechanical systems (MEMS and NEMS); furthermore, high-precision measurements of nanomechanical motion are broadly used to study fundamental phenomena in physics and biology. Therefore, development of nanomechanical motion transducers with high sensitivity and bandwidth has been a central research thrust in the fields of MEMS and NEMS. Here, we will review recent progress in this rapidly-advancing area.
Open Access
Nonlinear modeling of an immersed transmitting capacitive micromachined ultrasonic transducer for harmonic balance analysis
(IEEE, 2010) Oguz, H. K.; Olcum, S.; Senlik, M. N.; Taş, V.; Atalar, Abdullah; Köymen, Hayrettin
Finite element method (FEM) is used for transient dynamic analysis of capacitive micromachined ultrasonic transducers (CMUT) and is particularly useful when the membranes are driven in the nonlinear regime. One major disadvantage of FEM is the excessive time required for simulation. Harmonic balance (HB) analysis, on the other hand, provides an accurate estimate of the steady-state response of nonlinear circuits very quickly. It is common to use Mason's equivalent circuit to model the mechanical section of CMUT. However, it is not appropriate to terminate Mason's mechanical LC section by a rigid piston's radiation impedance, especially for an immersed CMUT. We studied the membrane behavior using a transient FEM analysis and found out that for a wide range of harmonics around the series resonance, the membrane displacement can be modeled as a clamped radiator. We considered the root mean square of the velocity distribution on the membrane surface as the circuit variable rather than the average velocity. With this definition, the kinetic energy of the membrane mass is the same as that in the model. We derived the force and current equations for a clamped radiator and implemented them using a commercial HB simulator. We observed much better agreement between FEM and the proposed equivalent model, compared with the conventional model.
Open Access
Optimization of the gain-bandwidth product of capacitive micromachined ultrasonic transducers
(IEEE, 2005-12) Olcum, S.; Senlik, M. N.; Atalar, Abdullah
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.
Open Access
A transimpedance amplifier design for capacitive micromachined ultrasonic transducers operating at 7.5MHz
(2021-01) İlhan, Giray
Capacitive Micromachined Ultrasonic Transducers (CMUTs) are MEMS devices used in ultrasound imaging, e.g. ultrasound mammography. CMUT proved to be a viable transducer solution in ultrasound mammography without the hazardous effects of conventional X-ray mammography. The CMUTs have a very high electrical impedance, where a transimpedance amplifier (TIA) is most appropriate for preamplification during reception. A TIA with 25MHz bandwidth and 120kΩ transimpedance gain is designed on Cadence Virtuoso using XFAB XC06M3 process. The CMUT small signal model is used for 50μm radius and 7.5MHz operating frequency. This model is incorporated into TIA circuit simulations. Two design options are proposed for the TIA, one with the passive feedback resistor and the other with a MOSFET feedback resistor. The latter enabled us to save space in layout design compare to the former. Transient and noise simulations are conducted and compared for schematic and layout views. The input referred current noise of the TIA is simulated to be 0.5pA/√Hz and the power consumption is simulated to be approximately 3.3mW for both designs.