Dissertations / Theses: 'Large Signal'

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Maki, D. W. "Large signal modelling of mixers." Thesis, University of Leeds, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355930.

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Garverick, Steven Lee. "Large signal linearity of scaled MOS transistors." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/14931.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1987.
MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING
Includes bibliographies.
by Steven L. Garverick.
Ph.D.

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Amaeshi, Lawrence Lemchukwu Nnanyelugo. "Large signal characterization of microwave GaAs MESFETs." Thesis, University of Surrey, 1988. http://epubs.surrey.ac.uk/843717/.

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Large Signal modelling of GaAs MESFETs has often been based on the device material and electrical parameters. This approach, while helping in elucidating the physics of the device, does not help the device user very much. There is the problem of modelling and computation complexity, and of simulation time. Furthermore predictions based on such models may not be consistent with practical reality. A real-time large Rf signal characterization of the device, will help in the understanding of the device behaviour under Large Signal drive, and would also yield valuable results/information, useful to the device designer and user, especially in Large Signal applications. A large Rf signal characterization of GaAs MESFETs, employing Large Signal S-parameter (LSSP), and waveform distortion analysis techniques, is carried out. LSSP design is a natural extension of the SSSP approach where the LSSPs are known. And the LSSP design approach is simplified if the LSSPs are determined easily. Waveform distortions affect the device performance. A LSSP measurement system, (also applicable to SSSP measurements), including an uncomplicated, direct deembedding technique is developed. A direct technique of measuring the current and voltage waveforms of the microwave signals, at the device terminals, is also developed. Measurements of the LSSPs show that only the input parameters: S21 and S11 vary with the Rf. The results are explained against reported trends of variation. The non-linear elements are identified, and a subsequent Large Signal Model (LSM) of the DUTs developed and verified. It is demonstrated that LSMs cannot be generalised. However a systematic approach of determining the LSM of a given device is given. An improved model of the transconductance, Gm, in terms of the S-parameters, and a method to determine the LSSP from small signal parameters are developed and verified. The optimum incident Rf to determine the LSSPs at a given bias is given. The flow of forward conduction,IF is known to damage, by burn-out, the DUT. A limiting resistor was included in the gate external circuit to limit this effect, when large enough Rf was employed. The interaction of the IF with this circuit is investigated, and the self-limiting actions explained. The flow of Is. is found to degrade the output performance and device power added efficiency also. The waveform distortions are investigated, the main causes - the nonlinear elements, and the manner in which they affect the distortions are explored. The non-linearity in the Gm is shown to be the main cause of the output waveform distortion, especially before the onset of forward conduction by the gate Schottky diode. While the forward conduction If and the non-linearity in the depletion capacitance are responsible for the input waveform distortion, hence are secondary causes of output waveform distortions. In particular, the flow of If, due to large Vgs > 0, causes the saturation of the drain voltage, hence the output power. But the waveforms, were in particular insensitive to the output conductance. The results reaffirm the LSM developed. Finally future work is discussed.

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Raghavan, Arvind. "Bipolar large-signal modeling and power amplifier design." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/13294.

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Hofer, Heiko. "Large-Scale Gradual Change Detection." Neubiberg Universitätsbibliothek der Universität der Bundeswehr, 2010. http://d-nb.info/1001920856/34.

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Bordelon, John H. "A large-signal model for the RF power MOSFET." Diss., Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/15048.

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Srivastava, Y. "Large signal modelling of coupled-cavity travelling wave tubes." Thesis, Lancaster University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379740.

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Senadji, Bouchra. "Méthodes évolutives de localisation de sources large bande /." Paris : Ecole nationale supérieure des Télécommunications, 1994. http://catalogue.bnf.fr/ark:/12148/cb35723464r.

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Lei, Chi-un, and 李志遠. "VLSI macromodeling and signal integrity analysis via digital signal processing techniques." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B45700588.

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Bebek, Gürkan. "Analyzing and modeling large biological networks inferring signal transduction pathways /." online version, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=case1157723743.

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Clausen, William. "Small and large signal modeling of MM-Wave MHEMT devices." [Tampa, Fla.] : University of South Florida, 2003. http://purl.fcla.edu/fcla/etd/SFE0000177.

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Bebek, Gurkan. "Analyzing and Modeling Large Biological Networks: Inferring Signal Transduction Pathways." Case Western Reserve University School of Graduate Studies / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=case1157723743.

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Youngseo, Ko. "Multi-Harmonic Broadband Measurement with an Large-Signal Network Analyzer." The Ohio State University, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=osu1268237958.

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Someswaran, Preethi. "Large Signal Modelling of AlGaN/GaN HEMT for Linearity Prediction." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1440392889.

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Sorgüven, Esra. "A computational aeroacoustics method using large eddy simulation and acoustic analogy /." Osnabrück : Der Andere Verl, 2004. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=016591660&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.

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Bottrell, Nathaniel. "Small-signal analysis of active loads and large-signal analysis of faults in inverter interfaced microgrid applications." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/24658.

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Rectifiers and voltage regulators that have characteristics of constant power loads may form a significant percentage of a microgrid's total loads. The real part of the input impedance of a constant power load is negative and it may have control loop dynamics in a similar frequency range to the inverters that are supplying the microgrid. This thesis examines the interactions between an active constant power load and a microgrid for the impact on stability. Participation analysis of the eigenvalues that result from the model of the combined microgrid and active load identified that the low-frequency modes are associated with the voltage controller of the active rectifier and the droop-controllers of the inverters. The analysis also revealed that when the active load dc-voltage controller is designed with large gains, the voltage controller of the inverter becomes unstable but the low frequency modes associated with the droop controller of the inverter remain stable. The transient stability of a microgrid may require that the inverter-interfaced generation remain connected during a fault and return to normal power export once a fault is cleared. For an inverter to supply fault current, the controller of the inverter must current-limit the output and the fault strategy chosen must ensure that the current and voltage limiter do not latch-up and that the controller integrators do not wind-up. This thesis analyses different limiting and reset strategies and concluded that that it is not possible to successfully reset a limiter when using a reset signal from a closed-loop controller within the inverter. In a system where there are cascaded limiters, successful operation is obtained when the inner limit is a saturation limiter and the output limiter is a set-reset limiter. It was found that the transient stability of an inverter interfaced microgrid using a droop control algorithm is dependent on the current limiter and inductance of the network.

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Dahmani, Samir [Verfasser]. "Large-Size AlGaN/GaN HEMT Large-Signal Electrothermal Characterization and Modeling for Wireless Digital Communications / Samir Dahmani." Kassel : Universitätsbibliothek Kassel, 2012. http://d-nb.info/102242274X/34.

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Jarndal, Anwar Hasan. "Large-signal modeling of GaN device for high power amplifier design." Kassel Kassel Univ. Press, 2006. http://www.upress.uni-kassel.de/publi/abstract.php?978-3-89958-258-1.

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Mengistu, Endalkachew Shewarega. "Large-signal modeling of GaN HEMTs for linear power amplifier design /." Kassel : Kassel Univ. Press, 2008. http://d-nb.info/987878476/04.

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Glaser, John Stanley 1964. "Topics in large-signal behavior of power electronic converters and systems." Diss., The University of Arizona, 1996. http://hdl.handle.net/10150/282217.

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A variety of topics in large-signal and system-level power electronics are explored. First, the load-sharing problem for converters with parallel- and series-connected outputs is defined and explained. Requirements for load-sharing behavior are illustrated graphically. Many classes of switching converters are capable of load-sharing aside from current-programmed-mode (CPM) converters, including but not limited to discontinuous-mode (DCM) pulse-width-modulated (PWM) converters and resonant converters. The input filter problem is studied for high-power-factor rectifiers (HPFRs) based on the DCM flyback converter. Such HPFRs require an input filter to reduce switching noise conducted to the AC line, but the filter can degrade the power factor and interfere with converter operation. The analysis allows filter design that minimizes and balances these effects. Intuitive and analytical approaches are given and compared. The analytical approach uses phase plane methods usually used for resonant converter analysis. Although the filter design is for a specific converter, the approach is applicable to any HPFR. A single-quadrant negative resistor is synthesized from a DCM flyback converter. This circuit is simple, efficient, and can handle power levels over 100W. A design procedure and small-signal analysis are given. Additionally, a set of large-signal dynamic circuit models are presented for DCM PWM converters. A general impedance synthesizer is developed based on a four-quadrant switching converter. This circuit is used to create the negative resistance pseudoinverter, which puts power onto the AC line for sale to a utility. To develop the pseudoinverter, the concept of load reduction is employed. Potential stability problems are studied and a solution implemented. The synthesis of self-contained reactive components is also studied. Extensive experimental verification substantiates the majority of the concepts in this dissertation. Simulation is also used to support some of the analysis.

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Chan, kwong Fu. "Large-signal characterization/modeling and linearization techniques for RF power amplifiers /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?ELEC%202004%20CHANK.

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Payakapan, Tassanee 1976. "Large-signal modeling of bulk and SOI RF power LDMOS FETs." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/86526.

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Thesis (S.B. and M.Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.
Includes bibliographical references (p. 83-86).
by Tassanee Payakapan.
S.B.and M.Eng.

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Hickish, Jack. "Digital signal processing methods for large-N, low-frequency radio telescopes." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:7d983fb3-9411-4906-92cd-70e2c1040b54.

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Current attempts to make precision measurements of the HI power spectrum at high redshifts have led to the construction of several low-frequency, large-N, interferometric arrays. The computational demands of digital correlators required by these arrays present a significant challenge. These demands stem from the treatment of radio telescopes as collections of two-element interferometers, which results in the need to multiply O(N²) pairs of antenna signals in an N-element array. Given the unparalleled flexibility offered by modern digital processing systems, it is apt to consider whether a different way of treating the signals from antennas in an array might be fruitful in current and future radio telescopes. Such methods potentially avoid the unfavourable N² scaling of computation rate with array size. In this thesis I examine the prospect of using direct-imaging methods to map the sky without first generating correlation matrices. These methods potentially provide great computational savings by creating images using efficient, FFT-based algorithms. This thesis details the design and deployment of such a system for the Basic Element of SKA Training II (BEST-2) array in Medicina, Italy. Here the 32-antenna BEST-2 array is used as a test bed for comparison of FX correlation and direct-imaging systems, and to provide a frontend for a real-time transient event detection pipeline. Even in the case of traditional O(N²) correlation methods, signal processing algorithms can be significantly optimized to deliver large performance gains. In this thesis I present a new mechanism for optimizing the cross-correlation operation on Field Programmable Gate Array (FPGA) hardware. This implementation is shown to achieve a 75% reduction in multiplier usage, and has a variety of benefits over existing optimization strategies. Finally, this thesis turns its focus towards The Square Kilometre Array (SKA). When constructed, the SKA will be the world's largest radio telescope and will comprise a variety of arrays targeting different observing frequencies and science goals. The low-frequency component of the SKA (SKA-low) will feature ~250,000 individual antennas, sub-divided into a number of stations. This thesis explores the impact of the station size on the computational requirements of SKA-low, investigating the optimal array configuration and signal processing realizations.

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Call, John B. "Large-signal characterization and modeling of nonlinear devices using scattering parameters." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/35548.

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Characterization and modeling of devices at high drive levels often requires specialized equipment and measurement techniques. Many large-signal devices will never have traditional nonlinear models because model development is expensive and time-consuming. Due to the complexity of the device or the size of the application market, nonlinear modeling efforts may not be cost effective. Scattering parameters, widely used for small-signal passive and active device characterization, have received only cursory consideration for large-signal nonlinear device characterization due to technical and theoretical issues. We review the theory of S-parameters, active device characterization, and previous efforts to use S-parameters with large-signal nonlinear devices. A robust, calibrated vector-measurement system is used to obtain device scattering parameters as a function of drive level. The unique measurement system architecture allows meaningful scattering parameter measurements of large-signal nonlinear devices, overcoming limitations reported by previous researchers. A three-port S-parameter device model, with a nonlinear reflection coefficient terminating the third port, can be extracted from scattering parameters measured as a function of drive level. This three-port model provides excellent agreement with device measurements across a wide range of drive conditions. The model is used to simulate load-pull data for various drive levels which are compared to measured data.
Master of Science

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Dey, Sourav. "Large-Signal Analysis of Buck and Interleaved Buck DC-AC Converters." Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1409578634.

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Jones, Paul. "Electrical measurement of large area substation earth grids." Thesis, Swansea University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367883.

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Deri, Joya A. "Graph Signal Processing: Structure and Scalability to Massive Data Sets." Research Showcase @ CMU, 2016. http://repository.cmu.edu/dissertations/725.

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Large-scale networks are becoming more prevalent, with applications in healthcare systems, financial networks, social networks, and traffic systems. The detection of normal and abnormal behaviors (signals) in these systems presents a challenging problem. State-of-the-art approaches such as principal component analysis and graph signal processing address this problem using signal projections onto a space determined by an eigendecomposition or singular value decomposition. When a graph is directed, however, applying methods based on the graph Laplacian or singular value decomposition causes information from unidirectional edges to be lost. Here we present a novel formulation and graph signal processing framework that addresses this issue and that is well suited for application to extremely large, directed, sparse networks. In this thesis, we develop and demonstrate a graph Fourier transform for which the spectral components are the Jordan subspaces of the adjacency matrix. In addition to admitting a generalized Parseval’s identity, this transform yields graph equivalence classes that can simplify the computation of the graph Fourier transform over certain networks. Exploration of these equivalence classes provides the intuition for an inexact graph Fourier transform method that dramatically reduces computation time over real-world networks with nontrivial Jordan subspaces. We apply our inexact method to four years of New York City taxi trajectories (61 GB after preprocessing) over the NYC road network (6,400 nodes, 14,000 directed edges). We discuss optimization strategies that reduce the computation time of taxi trajectories from raw data by orders of magnitude: from 3,000 days to less than one day. Our method yields a fine-grained analysis that pinpoints the same locations as the original method while reducing computation time and decreasing energy dispersal among spectral components. This capability to rapidly reduce raw traffic data to meaningful features has important ramifications for city planning and emergency vehicle routing.

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Warrington, E. Michael. "Ionospheric radiowave propagation effects observed with a large aperture antenna array." Thesis, University of Leicester, 1986. http://hdl.handle.net/2381/35817.

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The wavefronts of high frequency (HF) radio waves received after reflection from the ionosphere exhibit both spatial non-linearities and temporal variations which limit the performance of large aperture receiving arrays. The first objective of this investigation was to measure the phase and amplitude of ionospherically propagated signals at several widely spaced antennas in order to relate these parameters to the reflection process. From the amplitudes and phases measured at pairs of spaced antennas, the direction of arrival (DOA) of the signal in both azimuth and elevation was determined. Furthermore. by combining the DOA and reflection height measurements the transmitter location can be estimated from a single receiving site. The second objective of this study was to investigate the ability of the system to determine DOA and transmitter locations correctly. Two seven element antenna arrays were employed with maximum apertures of 1526 m and 294 m respectively. The associated multi-channel receiving and data logging equipment is described together with a pulsed sounding system employed for mode identification. Signals received from several European transmitters exhibited widely differing behaviour and this was interpreted in terms of their modal content. For predominantly single moded signals the observations indicate that the diffracted components normally contribute less than 10% of the received power, moreover the DOA varies in both azimuth and elevation by approximately 1-2° over time periods of several minutes. The use of the smaller array for DF and SSL applications is discussed in detail. In particular, the performance of the system was severly affected by multi-moded propagation. Techniques were developed for recognising periods of single moded propagation, when accurate measurements are to be expected. Good position fixes were obtained when measurements were restricted to these periods provided accurate reflection height information was also available.

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Burnett, Ronald. "Transient current analysis for fault detection in large induction motors." Thesis, Robert Gordon University, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318552.

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Salem, M. M. "Two level state estimation for large electric power systems." Thesis, University of Strathclyde, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372189.

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Azhar, Ahsan. "Large Signal RF Measurement Systems and Implementation of a Tuned Receiver System." Thesis, University of Gävle, Department of Technology and Built Environment, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-3102.

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This report shows a survey of sate of the art different large signal RF measurement systems. Such measurement systems are discussed in detail with respect to their architecture, method of measurement, calibration, accuracy, dynamic range and bandwidth. Finally, a RF measurement system for large signal was designed and implemented. This measurement system was based on a tuned receiver. Harmonic distortion type measurements were taken by this system and time domain waveforms were reconstructed using external software.

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Syed, Asad Abbas. "Large Signal Physical Simulations of Si LD-MOS transistor for RF application." Thesis, Linköping University, The Department of Physics, Chemistry and Biology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2627.

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The development of computer aided design tools for devices and circuits has increased the interest for accurate transistor modeling in microwave applications. In the increasingly expanding wireless communication market, there is a huge demand for high performance RF power devices. The silicon LD- MOSFET transistor is dueto its high power performance is today widely used in systems such as mobile base stations, private branch exchanges (PBX), and local area networks (LAN) utilizing the bands between 0.9 to 2.5 GHz.

In this research we simulated LD-MOSFET transistor characteristics of the structure provided by Infineon technology at Kista, Stockholm. The maximum drain current obtained in the simulation was 400 mA at a gate voltage of 8 V. This value is somewhat higher than the measured one. This difference can be attributed to the parasitic effects since no parasitic effects were included in the simulations in the beginning. The only parasitic effect studied was by placing the source contact at the bottom of the substrate according to real commercial device. The matching between simulated and measured results were improved and maximum drain current was reduced to 300 mA/mm which was 30% higher than the measured drain current

The large signal RF simulations were performed in time-domain in our novel technique developed at LiU. This technique utilizes a very simple amplifier circuit without any passive components. Only DC bias and RF signals are applied to the gate and drain terminals, with the same fundamental frequency but with 180o phase difference. The RF signal at the drain acting as a short at higher harmonics. These signals thus also acted as an active match to the transistor. Large signal RF simulations were performed at 1, 2 and 3 GHz respectively. The maximum of drain current signal was observed at the maximum of drain voltage signal indicating the normal behavior of the transistor. At 1 GHz the output power was 1.25 W/mm with 63% of drain efficiency and 23.7 dB of gain. The out pout power was decreased to 1.15 W/mm and 1.1 W/mm at 2 and 3 GHz respectively at the same time the efficiency and gain was also decreased to 57% and 19 dB at 2 GHz and 51% and 15 dB at 3GHz respectively.

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Browne, Jefferson Andrew. "A 2.5-D large-signal gain coupled-cavity travelling-wave tube model." Thesis, Lancaster University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.322520.

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Sporea, Radu. "Polysilicon thin-film source-gated transistors for mixed signal large area electronics." Thesis, University of Surrey, 2010. http://epubs.surrey.ac.uk/782735/.

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Sanchez, Juan Eusebio. "Semiconductor device simulation of low-frequency noise under periodic large-signal conditions." [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE1001178.

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Li, Kejiong. "Indoor and outdoor location estimation in large areas using received signal strength." Thesis, Queen Mary, University of London, 2013. http://qmro.qmul.ac.uk/xmlui/handle/123456789/8537.

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Location estimation when deployed on wireless networks supports a range of services including user tracking and monitoring, health care support and push and pull marketing. The main subject of this thesis is improving indoor and outdoor location estimation accuracy using received signal strength (RSS) from neighbouring base stations (BSs) or access points (APs), without using the global positioning system (GPS) or triangulation methods. For the outdoor environment, state-of-the-art deterministic and probabilistic algorithms are adapted to exploit principal components (PCs) and clustering. The accuracy is compared with K-nearest neighbour (KNN) algorithms using different partitioning models. The proposed scheme clusters the RSS tuples based on deviations from an estimated RSS attenuation model and then transforms the raw RSS in each cluster into new uncorrelated dimensions, using PCs. As well as simple global dimensionality reduction using PCs, the data reduction and rotation within each cluster improves estimation accuracy because a) each cluster can model the different local RSS distributions and b) it efficiently preserves the RSS correlations that are observed (some of which are substantial) in local regions and which independence approximations ignore. Different simulated and real environments are used for the comparisons. Experimental results show that positioning accuracy is significantly improved and fewer training samples are needed compared with traditional methods. Furthermore, a technique to adjust RSS data so that radio maps collected in different environmental conditions can be used together to enhance accuracy is also demonstrated. Additionally, in the radio coverage domain, a non-parametric probability approach is used for the radio reliability estimation and a semi-supervised learning model is proposed for the monitoring model training and evolution according to real-time mobile users’ RSS feedback. For the indoor environment, an approach for a large multi-story indoor location estimaiii tion using clustering and rank order matching is described. The accuracies using WiFi RSS alone, cellular GSM RSS alone and integrated WiFi and GSM RSS are presented. The methods were tested on real indoor environments. A hierarchical clustering method is used to partition the RSS space, where a cluster is defined as a set of mobile users who share exactly the same strongest RSS ranking set of transmitters. The experimental results show that while integrating of WiFi RSS with GSM RSS creates a marginal improvement, the GSM data can be used to ameliorate the loss of accuracy when APs fail.

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JUNIOR, ALEXANDRE AMORIM PEREIRA. "REVERSE LINK LARGE SCALE MIMO SIGNAL DETECTION WITH MULTIPLE USERS AND CELLS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2017. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=30898@1.

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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
INSTITUTO MILITAR DE ENGENHARIA
CENTRO TECNOLÓGICO DO EXÉRCITO
PROGRAMA DE EXCELENCIA ACADEMICA
Este trabalho tem como finalidade estudar o problema da detecção de usuários no canal reverso de sistemas MIMO de larga escala, que são caracterizados pelo elevado número de elementos de transmissão e recepção, com foco na complexidade computacional e no desempenho em termos de taxa de erro destes sistemas. Inicialmente, os algoritmos de detecção da família Likelihood Ascent Search (LAS) são investigados e é desenvolvido um novo algoritmo de detecção, denominado de Random-List Based LAS (RLBLAS), capaz de atingir melhores taxas de erros com menor complexidade computacional do que os demais detectores considerados. Posteriormente, técnicas de detecção e decodificação iterativas (Iterative Detection and Decoding - IDD) em sistemas MIMO foram analisadas de forma a propor uma estratégia IDD de complexidade computacional reduzida a fim de viabilizar a sua aplicação em cenários massivos. Finalmente, o problema da contaminação por pilotos em sistemas MIMO multicelulares de larga escala, um dos principais limitadores do desempenho desse tipo de sistema, é estudado e estratégias de detecção com cooperação parcial entre as estações base componentes do sistema que visam mitigar os efeitos da contaminação por pilotos são propostas. As análises e afirmações realizadas durante a presente tese são sustentadas por resultados de simulações de Monte Carlo dos sistemas de comunicações em diversos cenários distintos, incluindo os casos em que são considerados os efeitos de correlação entre as antenas de transmissão/recepção, os efeitos de sombreamento e os erros de estimação dos estados dos canais de comunicações envolvidos.
This work focuses on the multi-user multi-cellular large-scale MIMO reverse channel detection problem, where the number of transmitting and receiving antenna elements grows to the order of hundreds. In these scenarios, one major issue is the computational complexity of such systems. Therefore, this thesis aims to propose low-complexity techniques with good BER performance for the reverse channel detection of MIMO systems. Initially, the detection algorithms of the Likelihood Ascent Search (LAS) family are investigated and a new LAS based detector is proposed. This new detector, named Random-List Based LAS (RLB-LAS), is capable of achieving better BER with lower complexity then the other considered detectors. Next, iterative detection and decoding (IDD) techniques are analyzed in order to propose an IDD strategy applied to the detection and decoding of the reverse MIMO channel with reduced complexity to make possible its application to massive scenarios. Finally, the pilot contamination problem in multi-cellular large-scale MIMO systems, one of the major bounds on BER performance of these systems, are studied and some cooperative strategies are proposed in order to reduce the effects of this type of impairments. The analysis and statements of this thesis are supported by Monte Carlo simulation results of the considered systems in different scenarios, including the cases where the effects of transmitting and receiving antenna correlation, log-normal shadowing, and the estimation errors on the channel state information acquisition are considered.

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Choi, Byungcho. "Large signal transient analysis of duty ratio controlled DC-to-DC converter." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/43966.

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The large-signal transient response of duty ratio controlled dc-to-dc converters is investigated using the phase-plane technique. The transition pattern of large-signal trajectories is provided in terms of the circuit parameter and operating conditions. Several transient trajectories of practical interest including start-up, step input voltage change and step-load change are analyzed. The effect of large-signal characteristics of the feedback controller on the transient trajectory is presented.
Master of Science

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Keller, Donald Michael. "Frequency-domain analysis of memoryless nonlinearities having large-signal, almost periodic excitations." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/53547.

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Numerical frequency-domain techniques are widely used for the a.c. steady-state analysis of nonlinear electric circuits. Such techniques require that one compute the Fourier series for the response of each nonlinear circuit element, given a known excitation. Current approaches to this computation encounter difficulty when the response is almost periodic (that is, when the frequencies in its Fourier series are not all harmonically related), especially when the nonlinear characteristic is abrupt and the Fourier series for the response contains many significant terms. This dissertation develops an alternative approach that is theoretically sound and computationally efficient, for the important special case of a memoryless nonlinearity described by a continuous, bounded function. To begin the development, basic properties of almost periodic functions are presented. It is proven that the response of a memoryless nonlinearity is almost periodic whenever the excitation is. Next, the concept of a basis for a set of frequencies is introduced. The frequency content of the response is investigated, and it is proven that the frequencies in the response have the same basis as those in the excitation. The Fourier series for an almost periodic function is discussed, and its coefficients are expressed as mean values taken over an infinite interval. Results are given for the summability of the series. Starting with a theorem from Diophantine Approximation, it is proven that the normalized (Hertzian) phases corresponding to a set of M basis frequencies have their fractional parts uniformly distributed in an M-dimensional unit cube. This property of uniform phase distribution is then used to convert the single-dimensional integral for the Fourier series coefficients into a multiple integral over the unit cube, with the dimension of the integral equal to the number of basis frequencies in the Fourier series. A multi-dimensional extension of the Discrete Fourier Transform is used to evaluate the multiple integral, and expressions for aliasing are derived. It is shown that the multiple integral formulation compares favorably with existing approaches, and several numerical examples are presented to illustrate this formulation's capabilities.
Ph. D.

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40

Ngo, Hien Quoc. "Performance Bounds for Very Large Multiuser MIMO Systems." Licentiate thesis, Linköpings universitet, Kommunikationssystem, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-85240.

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The last ten years have seen significant advances of multiuser MIMO (MU-MIMO) in wireless communication. MU-MIMO is now being introduced in several new generation wireless standards (e.g.,LTE-Advanced, 802.16m). The number of users is increasing with more and more applications. At the same time, high transmission data rate and communication reliability are required. Furthermore, there is a growing concern about green communication which relates to the effects of the radiation emitted from wireless devices onthe human body. Therefore, the future MU-MIMO systems have to satisfy three main requirements: i) serving many autonomous users in the same time-frequency resource, ii) having high data rate and communication reliability, and iii) less energy consumption/radiation. These are seemingly contradictory requirements since the more users are served, the more interference the systems will suffer, or the more data rate is transmitted, the more power is required. MU-MIMO with very large antenna arrays seems to meet above demands and hence, it can be considered as a promising technology for next generation wireless systems. With very large antenna arrays (we mean arrays comprising say a hundred of antennas), the channel vectors are nearly-orthogonal and hence, multiuser interference can be significantly reduced. As a result, many users can be simultaneously served with high data rate. In particular, with coherent processing, transmit power can be reduced dramatically owing to array gain. In this thesis, we focus on the performance bounds of MU-MIMO with very large antenna arrays. We study the fundamental limits on the system performance when using large antenna arrays under practical constraints such as low complexity processing, imperfect channel state information, intercell interference, and finite-dimensional channels.

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41

Ahmed, Sara Mohamed. "Modeling of Power Electronics Distribution Systems with Low-frequency, Large-signal (LFLS) Models." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/27787.

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This work presents a modeling methodology that uses new types of models called low-frequency, large-signal models in a circuit simulator (Saber) to model a complex hybrid ac/dc power electronics system. The new achievement in this work is being able to model the different components as circuit-based models and to capture some of the large-signal phenomena, for example, real transient behavior of the system such as startup, inrush current and power flow directionality. In addition, models are capable of predicting most low frequency harmonics only seen in real switching detailed models. Therefore the new models system can be used to predict steady state performance, harmonics, stability and transients. This work discusses the modeling issues faced based on the author recent experiences both on component level and system level. In addition, it recommends proper solutions to these issues verified with simulations. This work also presents one of the new models in detail, a voltage source inverter (VSI), and explains how the model can be modified to capture low frequency harmonics that are usually phenomena modeled only with switching models. The process of implementing these different phenomena is discussed and the model is then validated by comparing the results of the proposed low frequency large signal (LFLS) model to a complete detailed switching model. In addition, experimental results are also obtained with a 2 kW voltage source inverter prototype to validate the proposed improved average model (LFLS model). In addition, a complete Verification, Validation, and Uncertainty Quantification (VV&UQ) procedures is applied to a two-level boost rectifier. The goal of this validation process is the improvement of the modeling procedure for power electronics systems, and the full assessment of the boost rectifier model predictive capabilities. Finally, the performance of the new models system is compared with the detailed switching models system. The LFLS models result in huge cut in simulation time (about 10 times difference) and also the ability to use large time step with the LFLS system and still capture all the information needed. Even though this low frequency large signal (LFLS) models system has wider capabilities than ideal average models system, it still can’t predict all switching phenomena. Therefore, another benefit of this modeling approach is the ability to mix different types of models (low frequency large signal (LFLS) and detailed switching) based on the application study they are used for.
Ph. D.

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42

Chen, Xin. "Ensemble methods in large vocabulary continuous speech recognition." Diss., Columbia, Mo. : University of Missouri-Columbia, 2008. http://hdl.handle.net/10355/5797.

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Thesis (M.S.)--University of Missouri-Columbia, 2008.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on August 28, 2008) Vita. Includes bibliographical references.

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43

Kilinc-Karzan, Fatma. "Tractable relaxations and efficient algorithmic techniques for large-scale optimization." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/41141.

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In this thesis, we develop tractable relaxations and efficient algorithms for large-scale optimization. Our developments are motivated by a recent paradigm, Compressed Sensing (CS), which consists of acquiring directly low-dimensional linear projections of signals, possibly corrupted with noise, and then using sophisticated recovery procedures for signal reconstruction. We start by analyzing how to utilize a priori information given in the form of sign restrictions on part of the entries. We propose necessary and sufficient on the sensing matrix for exact recovery of sparse signals, utilize them in deriving error bounds under imperfect conditions, suggest verifiable sufficient conditions and establish their limits of performance. In the second part of this thesis, we study the CS synthesis problem -selecting the minimum number of rows from a given matrix, so that the resulting submatrix possesses certifiably good recovery properties. We express the synthesis problem as the problem of approximating a given matrix by a matrix of specified low rank in the uniform norm and develop a randomized algorithm for this problem. The third part is dedicated to efficient First-Order Methods (FOMs) for large-scale, well-structured convex optimization problems. We propose FOMs with stochastic oracles that come with exact guarantees on solution quality, achieve sublinear time behavior, and through extensive simulations, show considerable improvement over the state-of-the-art deterministic FOMs. In the last part, we examine a general sparse estimation problem -estimating a block sparse linear transform of a signal from the undersampled observations of the signal corrupted with nuisance and stochastic noise. We show that an extension of the earlier results to this more general framework is possible. In particular, we suggest estimators that have efficiently verifiable guaranties of performance and provide connections to well-known results in CS theory.

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Twigg, Christopher M. "Floating Gate Based Large-Scale Field-Programmable Analog Arrays for Analog Signal Processing." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11601.

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Large-scale reconfigurable and programmable analog devices provide a new option for prototyping and synthesizing analog circuits for analog signal processing and beyond. Field-programmable analog arrays (FPAAs) built upon floating gate transistor technologies provide the analog reconfigurability and programmability density required for large-scale devices on a single integrated circuit (IC). A wide variety of synthesized circuits, such as OTA followers, band-pass filters, and capacitively coupled summation/difference circuits, were measured to demonstrate the flexibility of FPAAs. Three generations of devices were designed and tested to verify the viability of such floating gate based large-scale FPAAs. Various architectures and circuit topologies were also designed and tested to explore the trade-offs present in reconfigurable analog systems. In addition, large-scale FPAAs have been incorporated into class laboratory exercises, which provide students with a much broader range of circuit and IC design experiences than have been previously possible. By combining reconfigurable analog technologies with an equivalent large-scale digital device, such as a field-programmable gate array (FPGA), an extremely powerful and flexible mixed signal development system can be produced that will enable all of the benefits possible through cooperative analog/digital signal processing (CADSP).

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45

Shoubaki, Ehab Hamed. "UNIFIED LARGE AND SMALL SIGNAL DISCRETE-SPACE MODELING FOR PWM CONVERTERS IN CCM." Master's thesis, University of Central Florida, 2005. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3961.

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In this Thesis a Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulations of the converter switches , and this approach results in a small signal discrete model. The Second approach is direct and does not involve any approximation of the modulations , this approach yields both a large signal nonlinear discrete model and a linear small signal model. Harmonic analysis of the converter states at steady-state is done for steady-state waveform acquisition , which increases the accuracy of the model especially for finding the control to inductor current frequency response. Finally the Discrete model is verified for the Half-Bridge DC/DC topology for its three main control schemes (Asymmetric , Symmetric , DCS). A GUI platform in MATLAB is presented as a wrapper that utilizes the models and analysis presented in this thesis.
M.S.E.E.
Department of Electrical and Computer Engineering
Engineering and Computer Science
Electrical Engineering

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46

Shaiek, Hmaied. "Optimisation des performances d'enceintes co-axiales large bande par traitement numerique du signal." Brest, 2007. http://www.theses.fr/2007BRES2011.

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L'objectif de cette thèse est d'optimiser le rayonnement de sources acoustiques haut de gamme en utilisant des techniques de traitement numériques du signal adaptées. Cette optimisation s'est effectuée en deux grandes étapes. La première étape concerne l'optimisation des caractéristiques de rayonnement en champ libre. Cette partie peut être vue comme étant la complémentarité entre une recherche purement électroacoustique permettant de mettre au point des sources acoustiques capables de reproduire la totalité de la bande des fréquences audibles ([20Hz, 20kHz]) avec une directivité contrôlée: c'est l'apport des sources co-axiales. D'autre part, une recherche dans le domaine du traitement numérique du signal permettant de corriger les défauts résiduels de ces sources et d'appuyer leurs performances en vue de se rapprocher au mieux de l'idéal point source théorique. Pour une source acoustique à voies co-axiales, comme pour toute autre source multivoies, le module de traitement numérique du signal, que nous avons développé et validé sur des systèmes Cabasse, assure en plus des fonctions classiques de mise en phase, de séparation de voies et d'égalisation, un contrôle avancé de la directivité permettant de corriger d'éventuelles dérives du rayonnement au niveau des bandes de fréquences de recouvrement des transducteurs qui constituent la source. La deuxième étape d'optimisation, est relative aux corrections des colorations induites par le local d'écoute, c'est-à-dire égalisation du canal acoustique. En effet, le problème de la correction automatique des réflexions multiples et de la réverbération acoustique a suscité de nombreuses recherches sans qu'une solution universelle ne soit retenue. Dans le contexte de la présente étude où les sources acoustiques utilisées excitent les modes de très basses fréquences du local d'écoute, nous nous sommes focalisé sur le traitement des basses fréquences. Dans ce cas, une méthode d'égalisation multipoints basses fréquences des réponses du local d'écoute a été introduite. Cette technique propose une synthèse automatisée de filtres à encoches permettant de corriger les pics communs aux réponses mesurées au niveau d'une certaine zone d'écoute. Le but étant d'aboutir à une maquette de faisabilité, l'ensemble des traitements a été implémenté sur un DSP qui a été judicieusement choisi en fonction des applications visées et de la complexité des traitements à réaliser
This thesis deals with the optimization of High-End multi-way loudspeaker systems radiation by using dedicated digital signal processing techniques. This optimization was carried out in two parts. The first part relates to the optimization of the free field radiated by the loudspeaker system. This part can be seen as a complementarity between an electro-acoustical survey which made it possible to design acoustic sources able to reproduce the entire audio band extending with a well controlled directivity : this is the contribution of coaxial loudspeaker systems. On the other hand, a research in the field of digital signal processing correcting the residual defects of these sources and enhancing their performances in order to approach as well as possible the theoretical point source. For a coaxial acoustic source, as for any other multi-way loudspeaker system, the digital filter bank we developed, and validated on Cabasse systems, ensures, in addition to the usual crossover and equalization functions, an enhanced control of the system directivity making it possible to correct possible radiation shifts over transducers' frequency overlap bands. The second part of optimization, relates to the transfer brought by the listening room : equalization of the Room Transfer Functions. Indeed, many researchers were concerned with the correction of multiple room reflections and acoustic reverberation. However no universal solution is adopted. In the context of this study where the acoustic sources stimulate the very low frequencies room modes, it was initially necessary to focus on solving this problem. In this case, a multiple-point low frequency compensation technique of the room modes effects was introduced. This method proposes an automated design of digital notch filters making it possible to correct the peaks that are common to all the room responses measured over a given listening zone. The goal being to lead to an industrial model, the whole processing were implemented in real-time on a DSP which was thoroughly chosen according to the applications targeted and the complexity of the processing to be carried out

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Wu, Yuanyuan. "HADOOP-EDF: LARGE-SCALE DISTRIBUTED PROCESSING OF ELECTROPHYSIOLOGICAL SIGNAL DATA IN HADOOP MAPREDUCE." UKnowledge, 2019. https://uknowledge.uky.edu/cs_etds/88.

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The rapidly growing volume of electrophysiological signals has been generated for clinical research in neurological disorders. European Data Format (EDF) is a standard format for storing electrophysiological signals. However, the bottleneck of existing signal analysis tools for handling large-scale datasets is the sequential way of loading large EDF files before performing an analysis. To overcome this, we develop Hadoop-EDF, a distributed signal processing tool to load EDF data in a parallel manner using Hadoop MapReduce. Hadoop-EDF uses a robust data partition algorithm making EDF data parallel processable. We evaluate Hadoop-EDF’s scalability and performance by leveraging two datasets from the National Sleep Research Resource and running experiments on Amazon Web Service clusters. The performance of Hadoop-EDF on a 20-node cluster improves 27 times and 47 times than sequential processing of 200 small-size files and 200 large-size files, respectively. The results demonstrate that Hadoop-EDF is more suitable and effective in processing large EDF files.

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Suh, Inwon. "Design, Modeling, and Noise Measurement of Oscillators Using a Large Signal Network Analyzer." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1307567431.

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Muralidharan, Pavithra [Verfasser], and Stefan van [Akademischer Betreuer] Waasen. "Digital Signal Processing and Mixed Signal Control of Receiver Circuitry for Large-Scale Particle Detectors / Pavithra Muralidharan ; Betreuer: Stefan van Waasen." Duisburg, 2020. http://d-nb.info/1210861526/34.

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BAPAT, SACHIN VASUDEO. "THE PERFORMANCE EVALUATION OF VHDL-AMS SIMULATORS BY CREATING LARGE, SCALABLE VHDL-AMS MODELS." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1032179532.

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Dissertations / Theses on the topic 'Large Signal'

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