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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Multilayer scalable coupler with high directivity

Basta, Nina Popovic 21 September 2015 (has links)
This thesis addresses the design, analysis, and experimental validation of a high-directivity and high coupling microwave directional coupler. The motivating application is in broadband signal routing between cores of multi-core processors, where the delay of simple wire interconnects introduces unacceptable latency. The performance goals include scalability with frequency, a coupling coefficient of 3 dB, directivity larger than 40 dB, high return loss, low insertion loss below 3 dB at the center frequency, and small footprint. The approach to this problem taken in the thesis is a combination of edge and broad-side coupling in a multi-layer, multi-conductor microstrip coupled-line system. The two coupling mechanisms between neighboring pairs of coupled lines, along with appropriate end interconnections, allow for reduced size and design that achieves equal propagation velocities for the different modes supported by the five-conductor guiding structure that contribute to coupling. To validate the approach, a coupler designed for operation at 1 GHz is demonstrated to have a isolation of -22 dB with a coupling coefficient of 3\,dB and a return loss of -20 dB. The coupler is implemented on a FR-408 substrate with a permittivity of 3.66 and 1.17mm and 0.17mm thicknesses, and a total area of 12.65 cm^2. Three metalization layers are used in the design, with edge and broad-side coupled pairs of lines on the top two layers and diagonal end interconnects between the top and bottom lines. The coupler design is then scaled to 3 GHz by shortening the coupled-line length, and established -24 dB isolation, coupling of 3 dB, return loss of -20 dB, and has a total area of 6.9 cm^2. The analysis of the coupler shows that full-wave electromagnetic modeling agrees well with measurements and is necessary during the design process, while circuit analysis with built-in coupled-line models shows poorer agreement with experimental data. A tolerance analysis shows that the coupler performance is most sensitive to milling precision and separation between coupled-lines. Based on the measured and simulated results, it is shown that this type of coupler can be further scaled to higher frequencies and on-chip implementations for signal distribution in multi-core processors, or any other application where a number of components need to be interconnected with low latency and no reflection.
2

Adaptive techniques for scalable video compression

Mehrseresht, Nagita, Electrical Engineering & communication, UNSW January 2005 (has links)
In this work we investigate adaptive techniques which can be used to improve the performance of highly scalable video compression schemes under resolution scaling. We propose novel content adaptive methods for motion compensated 3D discrete wavelet transformation (MC 3D-DWT) of video. The proposed methods overcome problems of ghosting and non-aligned aliasing artifacts, which can arise in regions of motion model failure, when the video is reconstructed at reduced temporal or spatial resolutions. We also study schemes which facilitate simultaneous scaling of compressed video bitstreams based on both constant bit-rate and constant distortion criteria, using simple and generic scaling operations. In regions where the motion model fails, the motion compensated temporal discrete wavelet transform (MC TDWT) causes ghosting artifacts under frame-rate scaling, due to temporal lowpass filtering along invalid motion trajectories. To avoid ghosting artifacts, we adaptively select between different lowpass filters, based on a local estimate of the motion modelling accuracy. Experimental results indicate that the proposed adaptive transform substantially removes ghosting artifacts while also preserving the high compression efficiency of the original MC TDWT. We also study the impact of various MC 3D-DWT structures on spatial scalability. Investigating the interaction between spatial aliasing, scalability and energy compaction shows that the t+2D structure essentially has higher compression efficiency. However, where the motion model fails, structures of this form cause non-aligned aliasing artifacts under spatial scaling. We propose novel adaptive schemes to continuously adapt the structure of MC 3D-DWT based on information available within the compressed bitstream. Experimental results indicate that the proposed adaptive structure preserves the high compression efficiency of the t+2D structure while also avoiding the appearance of non-aligned aliasing artifacts under spatial scaling. To provide simultaneous rate and distortion scaling, we study ???layered substream structure. Scaling based on distortion generates variable bit-rate traffic which satisfies the desired average bit-rate and is consistent with the requirements of leaky-bucket traffic models. We propose a novel method which also satisfies constraints on instantaneous bit-rate. This method overcomes the weakness of previous methods with small leaky-bucket buffer sizes. Simulation results indicate promising performance with both MC 3D-DWT interframe and JPEG2000 intraframe compression.
3

Adaptive techniques for scalable video compression

Mehrseresht, Nagita, Electrical Engineering & communication, UNSW January 2005 (has links)
In this work we investigate adaptive techniques which can be used to improve the performance of highly scalable video compression schemes under resolution scaling. We propose novel content adaptive methods for motion compensated 3D discrete wavelet transformation (MC 3D-DWT) of video. The proposed methods overcome problems of ghosting and non-aligned aliasing artifacts, which can arise in regions of motion model failure, when the video is reconstructed at reduced temporal or spatial resolutions. We also study schemes which facilitate simultaneous scaling of compressed video bitstreams based on both constant bit-rate and constant distortion criteria, using simple and generic scaling operations. In regions where the motion model fails, the motion compensated temporal discrete wavelet transform (MC TDWT) causes ghosting artifacts under frame-rate scaling, due to temporal lowpass filtering along invalid motion trajectories. To avoid ghosting artifacts, we adaptively select between different lowpass filters, based on a local estimate of the motion modelling accuracy. Experimental results indicate that the proposed adaptive transform substantially removes ghosting artifacts while also preserving the high compression efficiency of the original MC TDWT. We also study the impact of various MC 3D-DWT structures on spatial scalability. Investigating the interaction between spatial aliasing, scalability and energy compaction shows that the t+2D structure essentially has higher compression efficiency. However, where the motion model fails, structures of this form cause non-aligned aliasing artifacts under spatial scaling. We propose novel adaptive schemes to continuously adapt the structure of MC 3D-DWT based on information available within the compressed bitstream. Experimental results indicate that the proposed adaptive structure preserves the high compression efficiency of the t+2D structure while also avoiding the appearance of non-aligned aliasing artifacts under spatial scaling. To provide simultaneous rate and distortion scaling, we study ???layered substream structure. Scaling based on distortion generates variable bit-rate traffic which satisfies the desired average bit-rate and is consistent with the requirements of leaky-bucket traffic models. We propose a novel method which also satisfies constraints on instantaneous bit-rate. This method overcomes the weakness of previous methods with small leaky-bucket buffer sizes. Simulation results indicate promising performance with both MC 3D-DWT interframe and JPEG2000 intraframe compression.
4

Multimode Optomechanical Systems and Phononic Networks

Kuzyk, Mark 11 January 2019 (has links)
An optomechanical system consists of an optical cavity mode coupled to a mode of a mechanical oscillator. Depending on the configuration of the system, the optomechanical interaction can be used to drive or cool the mechanical mode, coherently swap the optical and mechanical states, or create entanglement. A multimode optomechanical system consists of many optical (mechanical) modes coupled to a mechanical (optical) mode. With the tools of the optomechanical interaction, multimode optomechanical systems provide a rich platform to study new physics and technologies. A central challenge in optomechanical systems is to mitigate the effects of the thermal environment, which remains significant even at cryogenic temperatures, for mechanical oscillators typically used in optomechanical systems. The central theme of this thesis is to study how the properties of multimode optomechanical systems can be used for such mitigation of thermal noise. The most straightforward extension of an optomechanical system to a multimode system is to have a single optical mode couple to two mechanical modes, or a single mechanical mode couple to two optical modes. In this thesis, we study both types of multimode system. In each case, we study the formation of a dark mode, an eigenstate of the three-mode system that is of particular interest. When the system is in a dark state, the two modes of similar character (optical or mechanical) interact with each other through the mode of dissimilar character, but due to interference, the interaction becomes decoupled from the properties of the dissimilar mode. Another interesting application of the three-mode system is two-mode optical entanglement, generated through mechanical motion. Such entanglement tends to be sensitive to thermal noise. We propose a new method for generating two-mode optical entanglement in the three-mode system that is robust against the thermal environment of the mechanical mode. Finally, we propose a novel, scalable architecture for a quantum computer. The architecture makes use of the concepts developed earlier in the thesis, and applies them to a system that on the surface looks quite different from the standard optomechanical system, but is formally equivalent. This dissertation includes previously published and unpublished coauthored material.
5

Etude et mise en oeuvre d'un système d'interaction adaptatif pour les applications de réalité virtuelle / Design and implementation of an adaptative interaction system for virtual reality applications

Frad, M'hamed 17 December 2016 (has links)
Dans les dernières décennies, la réalité virtuelle a connu un essor fulgurant dans de nombreuses disciplines. Elle permet via des paradigmes d’interaction et d’immersion de plonger l’utilisateur au cœur d’un environnement artificiel crée numériquement. Ces paradigmes s’appuient sur l’utilisation des interfaces sensori-motrices bien spécifiques qui permettent à l’utilisateur d’interagir et accomplir des tâches particulières dans l’environnement virtuel. Néanmoins, des nombreux problèmes, d’origine technologique, sont souvent présents et peuvent pénaliser la qualité de l’interaction ainsi que le degré d’immersion de l’utilisateur dans l’environnement virtuel.L’objectif de cette thèse est de proposer une procédure complète visant à guider l’utilisateur à calibrer une interface sensori-motrice spécifique et par conséquent tenter de pallier à certains défauts technologiques. L’originalité de la thèse réside dans l’utilisation d’une approche qui combine deux domaines de recherche qui ne s’associent que très rarement : celui du traitement de données et celui de la réalité virtuelle. Cette approche servira de cadre théorique et technique pour la conception d’une procédure de calibration complète permettant de garantir une interaction continue et précise dans l’environnement virtuel.Afin de contrebalancer les défauts et limites techniques, le travail a été conduit sur plusieurs fronts : acquisition, traitement de données et validation. La première phase est marquée par l’utilisation d’un protocole innovant dans la mesure où il repose sur les techniques de réalité virtuelle pour récolter les données de calibration. Dans la deuxième phase, deux techniques de calibration ont été proposées pour améliorer la précision absolue de l’interface de réalité virtuelle. Les deux techniques se distinguent par leurs qualités d’approximateurs universels ainsi que par leurs capacités à estimer les sorties du système concerné à partir des entrées sans connaître à priori son modèle mathématique. Dans la dernière phase, deux prototypes d’applications de réalité virtuelle ont été développées pour s’assurer de la pertinence de notre approche. / Over last decades, virtual reality has been widely used in many disciplines. It is able to plunge the user at the heart of an artificial environment created digitally through interaction and immersion paradigms. These paradigms are based on the use of very specific interfaces that help user to interact and performspecific tasks in the virtual environment. Nevertheless, many technical problems are often present and may penalize the quality of that interaction and may break user immersion in the virtual environment.The goal of this thesis is to build a comprehensive procedure to guide the user to calibrate a virtual reality interface and therefore attempt to overcome some technological shortcomings. The originality of the thesis is the use of an approach that combines two areas of research that will combine very rarely, that of data processing and the virtual reality. This approach will provide theoretical and technical framework for the design of a comprehensive calibration procedure to ensure continuous and precise interaction in the virtual environment.To overcome problems described above, the work was conducted on several fronts :data acquisition, processing and validation. The first step is by the use of a new protocol insofar as it is based on virtual reality techniques to collect calibration data. In second step, two calibration methods have been proposed to improve the absolute accuracy of the virtual reality interface. Both methods are universal approximators as well as their ability to estimate the outputs of the involved system from inputs even the model of the system being calibrated remains unknown. In the last step, two virtual reality applications prototypes were developed in order to assess the relevance of our approach.
6

Scalable Multimedia Communication using Network Coding

Shao, Mingkai 01 1900 (has links)
This dissertation devotes itself to algorithmic approaches to the problem of scalable multicast with network coding. Several original contributions can be concluded as follows. We have proved that the scalable multicast problem is NP-hard, even with the ability to perform network coding at the network nodes. Several approximations are derived based on different heuristics, and systematic approaches have been devised to solve those problems. We showed that those traditional routing methods reduce to a special case in the new network coding context. Two important frameworks usually found in traditional scalable multicast solutions, i.e. layered multicast and rainbow multicast, are studied and extended to the network coding scenario. Solutions based on these two frameworks are also presented and compared. Suprisingly, these two distinctive approaches in the traditional sense become connected and share a similar essence of data mixing in the light of network coding. Cases are presented where these two approaches become equivalent and achieve the same Performance. We have made significant advances in constructing good solutions to the scalable multicast problem by solving various optimization problems formulated in our approaches. In the layered multicast framework, we started with a straight-forward extension of the traditional layered multicast to the network coding context. The proposed method features an intra-layer network coding technique which is applied on different optimized multicast graphs. Later on, we further improved this method by introducing the inter-layer network coding concept. By allowing network coding among data from different data layers, more leverage is gained when optimizing the network flow, thus higher performance is achieved. In the rainbow multicast framework, we choose uneven erasure protection (UEP) technique as the practical way of constructing balanced MDC, and optimize this MDC design using the max-flow information of receivers. After the MDC design is finalized, a single linear network broadcast code is employed to deliver MDC encoded data to receivers while satisfying the individual max-flow of all the receivers. Although this rainbow multicast based solution may sacrifice the performance in some cases, it greatly simplifies the rate allocation problem raised in the layered multicast framework. The use of one single network code also makes the network codes construction process a lot clearer. Extensive amount of simulation is performed and the results show that network coding based scalable multicast solutions can significantly outperform those traditional routing based solutions. In addition to the imaginary linear objective function used in the simulation, the practical convex objective function and real video data are also used to verify the effectiveness of the proposed solutions. The role of different parameters in the proposed approaches are analyzed, which gives us more guidelines on how to fine-tune the system. / Thesis / Doctor of Philosophy (PhD)
7

Rate-distortion analysis and traffic modeling of scalable video coders

Dai, Min 12 April 2006 (has links)
In this work, we focus on two important goals of the transmission of scalable video over the Internet. The first goal is to provide high quality video to end users and the second one is to properly design networks and predict network performance for video transmission based on the characteristics of existing video traffic. Rate-distortion (R-D) based schemes are often applied to improve and stabilize video quality; however, the lack of R-D modeling of scalable coders limits their applications in scalable streaming. Thus, in the first part of this work, we analyze R-D curves of scalable video coders and propose a novel operational R-D model. We evaluate and demonstrate the accuracy of our R-D function in various scalable coders, such as Fine Granular Scalable (FGS) and Progressive FGS coders. Furthermore, due to the time-constraint nature of Internet streaming, we propose another operational R-D model, which is accurate yet with low computational cost, and apply it to streaming applications for quality control purposes. The Internet is a changing environment; however, most quality control approaches only consider constant bit rate (CBR) channels and no specific studies have been conducted for quality control in variable bit rate (VBR) channels. To fill this void, we examine an asymptotically stable congestion control mechanism and combine it with our R-D model to present smooth visual quality to end users under various network conditions. Our second focus in this work concerns the modeling and analysis of video traffic, which is crucial to protocol design and efficient network utilization for video transmission. Although scalable video traffic is expected to be an important source for the Internet, we find that little work has been done on analyzing or modeling it. In this regard, we develop a frame-level hybrid framework for modeling multi-layer VBR video traffic. In the proposed framework, the base layer is modeled using a combination of wavelet and time-domain methods and the enhancement layer is linearly predicted from the base layer using the cross-layer correlation.
8

Image Compression Using Wavelet Based Scalable Modeling of Residual Image

Lin, Wan-Shan 14 July 2000 (has links)
This thesis is based on the modified JPEG encoding which uses a preprocessing called as Cubic Convolution Spline Interpolation to subsample the original image into lower resolution image, the subsampled image is encoded by JPEG. The modified JPEG can get very high compression ratio, it¡¦s quality is better than the JPEG file which has the same compressing ratio, but it still is not good enough. In this thesis we use the scalable wavelet encoding to encode the residual image, which is the difference between original and compression image. Due to the high compressing ratio and scalablity. We can attach the compressed residual image with modified JPEG compressed image to get the scalable compressed image whose compressing ratio can tun from 125 to 50 and always get better quality than optimal JPEG.
9

Scalable Broadband Models for Spiral Inductors in Multilayer Organic Package Substrate

Chiu, Chi-tsung 30 July 2004 (has links)
The thesis consisted of three parts. The first part introduced designed trend of the embedded passive component and the process flow of organic substrate. A design flow of spiral inductor embedded in 4 layer organic substrate has been demonstrated. Part 2 focused on the extraction equations of conventional PI model and modified T model. These two models have been applied to develop the equivalent circuits of the organic spiral inductors . The comparison between modeling and measurement results shows their difference on modeling accuracy. Part 3 introduced the scalable equations in both modeling techniques to find the equivalent circuit parameters from inductor¡¦s geometrical parameters. A 2.4GHz band-pass filter was simulated to illustrate the application of wide band scalable modeling techniques.
10

A Frequency-scalable 14-bit ADC for Low Power Sensor Applications

Liang, Joshua 15 February 2010 (has links)
In this thesis, a 14-bit low-power Analog-to-Digital Converter (ADC) is designed for sensor applications. Following on previous work, the ADC is designed to be frequency scalable by 1000 times from 1.67S/s to 1.67kS/s. To reduce power, class AB opamps are used. The design was fabricated in 0.18um CMOS and occupies an area of 0.35mm2. Operating at full-rate as a Delta-Sigma modulator, the ADC achieves 91.8dB peak SNDR while consuming 83uW. In incremental mode, the ADC powers off periodically to achieve frequency scalability, maintaining 84.7dB to 89dB peak SNDR while operating from 1.67S/s to 1.67kS/s.

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