Browsing by Subject "Oscillator"
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Item Open Access Analysis of the generation of amplitude-squeezed light with Gaussian-beam degenerate optical parametric amplifiers(OSA Publishing, 2001-06) Köprülü, K. G.; Aytür, O.We investigate the generation of amplitude-squeezed states with degenerate optical parametric amplifiers that are pumped by focused Gaussian beams. We present a model that facilitates the calculation of the squeezing level for an experimentally realistic cofiguration in which there is a Gaussian input signal beam that has the same confocal parameter and waist location as the Gaussian pump beam, with no restriction on the interaction length-to-confocal parameter ratio. We show that the 3-dB squeezing limit that was thought to be imposed by the Gaussian pump profile can be exceeded in the (previously uninvestigated) tight-focusing regime. We find the maximum possible amplitude squeezing in this regime to be 4.65 dB. However, it is possible to increase the squeezing level further by spatially filtering the tails of the output signal beam, resulting in squeezing levels in excess of 10 dB. (C) 2001 Optical Society of America.Item Open Access Conewise linear systems: a characterization of transitive cones in 3D-space(The European Control Association (EUCA), 2019-06) Özgüler, A. Bülent; Zakwan, MuhammadA spatial (3D) piecewise linear system with multiple modes having conewise state spaces is considered. A single mode in this system is called transitive from one (respectively, two) of its borders if every trajectory that starts in its interior or at a border travels in its interior, hits that border (respectively, one of the two borders), and goes out of the cone. This paper characterizes transitive cones in case the dynamics in the cone is dictated by real and distinct eigenvalues. An example of a 3D piecewise linear system composed of transitive cones illustrates how a nonlinear oscillator can be synthesized.Item Open Access A micromachined pressure sensor(Bilkent University, 2017-09) Karaca, HasanCapacitive Micromachined Ultrasonic Transducer (CMUT) is a microelectromechanical device that is basically formed by a moving top electrode, a stable bottom electrode and a gap in between. In spite of its this simple mass-spring construction, CMUT is a nonlinear device and its working principles have been formulated. According to these studies, the top electrode can be set in motion by the applied pressure on it and by depending on the amount of that pressure, the resonant frequency of the CMUT can be altered. Therefore, it is possible to use CMUT to obtain a pressure sensor. In this respect, what we have to do is keep tracking of its resonant frequency to deduce the pressure. The most e ective way of doing it, on the other hand, is using an oscillator circuit which also provides us the capability of tracking the resonant frequency in real time. Also, to design an integrated circuit that works with the CMUT, the best way is utilizing a Colpitts oscillator. In this thesis, we design a pressure sensor with CMUT based Colpitts oscillator. In order to achieve our design, rst of all, we examine the small signal equivalent circuit model of an uncollapsed mode CMUT and investigate the related analytical equations that models the behavior of it. To simplify the equations, we liken the small signal equivalent circuit model to a crystal oscillator by making necessary transformations. After that, we investigate the \feedback system approach" and \negative resistance concept" methods that help us to analyze the oscillator circuits; and we determine the Colpitts oscillator circuit as the oscillator circuit part of our device. We evaluate the CMUT based Colpitts oscillator circuit and derive the limitations on the circuit parameters for achieving a power e cient device. In addition to that, we discuss the dc biasing of the oscillator circuit that does not cause any loading e ect on the oscillator circuit and design a ring oscillator and a charge pump circuit which help us to obtain bias voltage on the CMUT. Finally, we calculate the sensitivity (in Hz/Pa) and the temperature sensitivity of a CMUT in addition to the Quality factor of our circuit; and by being based on these calculations, we obtain the optimum CMUT parameters for the best available sensitivity and conclude the design. At the end, we design a CMUT based Colpitts oscillator that works as a pressure sensor which measures pressure between zero atm and one atm with sensitivity of 14.6 Hz/Pa at 1 atm. The selected CMUT parameters, on the other hand, for the radius of the CMUT cell, the gap height of the CMUT cell, the thickness of the insulator layer and the thickness of the top plate are 44 m, 100 nm, 100 nm and 3 m respectively. The Quality factor of the circuit is 5 and the inherent Quality factor of the CMUT is 432.Item 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.Item Open Access Observer-based control of a class of chaotic systems(Elsevier, 2001) Solak, E.; Morgül, O.; Ersoy, U.We consider the control of a class of chaotic systems, which covers the forced chaotic oscillators. We focus on two control problems. The first one is to change the dynamics of the system to a new one which exhibits a desired behavior, and the second one is the tracking problem, i.e., to force the solutions of the chaotic system to track a given trajectory. To solve these problems we use observers which could be used to estimate the unknown states of the system to be controlled. We apply the proposed method to the control of Duffing equation and the Van der Pol oscillator and present some simulation results. © 2001 Elsevier Science B.V.