1,402 research outputs found

    The reduced order model problem in distributed parameter systems adaptive identification and control

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    The research concerning the reduced order model problem in distributed parameter systems is reported. The adaptive control strategy was chosen for investigation in the annular momentum control device. It is noted, that if there is no observation spill over, and no model errors, an indirect adaptive control strategy can be globally stable. Recent publications concerning adaptive control are included

    Transmitter Equalization for 4Gb/s Signalling

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    To operate a serial channel over copper wires at 4Gb/s, we incorporate an 4GHz FIR equalizing filter into a differential transmitter. The equalizer cancels the frequency-dependent attenuation caused by the skin-effect resistance of copper wire giving a frequency response that is flat to within 5% over the band from 200MHz to 2GHz even over wires with 6dB of high-frequency attenuation. All but the last stage of the transmitter operates at 400MHz. The transmitter output stage uses a stable 10-phase 400MHz clock to sequence an array of drivers that implement the FIR filter. This paper introduces the concept of digital-signal equalization, describes the system design and circuit design of our equalizing transmitter, and presents simulation results from a 4Gb/s 0.5µm CMOS transmitter. 1. Introduction The performance of many digital systems is limited by the interconnection bandwidth between chips, boards, and cabinets. As VLSI technology continues to scale, system bandwidth will become an ..

    Re-Sonification of Objects, Events, and Environments

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    abstract: Digital sound synthesis allows the creation of a great variety of sounds. Focusing on interesting or ecologically valid sounds for music, simulation, aesthetics, or other purposes limits the otherwise vast digital audio palette. Tools for creating such sounds vary from arbitrary methods of altering recordings to precise simulations of vibrating objects. In this work, methods of sound synthesis by re-sonification are considered. Re-sonification, herein, refers to the general process of analyzing, possibly transforming, and resynthesizing or reusing recorded sounds in meaningful ways, to convey information. Applied to soundscapes, re-sonification is presented as a means of conveying activity within an environment. Applied to the sounds of objects, this work examines modeling the perception of objects as well as their physical properties and the ability to simulate interactive events with such objects. To create soundscapes to re-sonify geographic environments, a method of automated soundscape design is presented. Using recorded sounds that are classified based on acoustic, social, semantic, and geographic information, this method produces stochastically generated soundscapes to re-sonify selected geographic areas. Drawing on prior knowledge, local sounds and those deemed similar comprise a locale's soundscape. In the context of re-sonifying events, this work examines processes for modeling and estimating the excitations of sounding objects. These include plucking, striking, rubbing, and any interaction that imparts energy into a system, affecting the resultant sound. A method of estimating a linear system's input, constrained to a signal-subspace, is presented and applied toward improving the estimation of percussive excitations for re-sonification. To work toward robust recording-based modeling and re-sonification of objects, new implementations of banded waveguide (BWG) models are proposed for object modeling and sound synthesis. Previous implementations of BWGs use arbitrary model parameters and may produce a range of simulations that do not match digital waveguide or modal models of the same design. Subject to linear excitations, some models proposed here behave identically to other equivalently designed physical models. Under nonlinear interactions, such as bowing, many of the proposed implementations exhibit improvements in the attack characteristics of synthesized sounds.Dissertation/ThesisPh.D. Electrical Engineering 201

    Multi-transit Echo Suppression for Passive Wireless Surface Acoustic Wave Sensors Using 3rd Harmonic Unidirectional Transducers and Walsh-Hadamard-like Reflectors

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    A passive wireless surface acoustic wave sensor of a delay-line type is composed of an antenna, a transducer that converts the EM signal into a surface acoustic wave, and a set of acoustic reflectors that reflect the incoming signal back out through the antenna. A cavity forms between the transducer and the reflectors, trapping energy and causing multiple unwanted echoes. The work in this dissertation aims to reduce the unwanted echoes so that only the main transit signal is left--the signal of interest with sensor information. The contributions of this dissertation include reflective delay-line device response in the form of an infinite impulse response (IIR) filter. This may be used in the future to subtract out unwanted echoes via post-processing. However, this dissertation will use a physical approach to echo suppression by using a unidirectional transducer. Thus a unidirectional transducer is used and also optimized for 3rd harmonic operation. Both the directionality and the coupling of the 3rd harmonic optimized SPUDT are improved over a standard electrode width controlled (EWC) SPUDT. New type of reflectors for the reflective delay-line device are also presented. These use BPSK type coding, similar to that of the Walsh-Hadamard codes. Two types are presented, variable reflectivity and variable chip-lengths. The COM model is used to simulate devices and compare the predicted echo suppression level to that of fabricated devices. Finally, a device is mounted on a tunable antenna and the echo is suppressed on a wireless operating device

    Design, stability and applications of two dimensional recursive digital filters

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    Imperial Users onl

    New sensor design and characterisation for electromagnetic tracking in image-guided interventions

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    Sistemi di localizzazione tramite campi elettromagnetici, o electromagnetic tracking (EMT) in inglese, trovano importanti applicazioni in ambiti sia medici che industriali. La tesi si concentra sullo studio e lo sviluppo di sensori magnetici per utilizzo in sistemi EMT. I principali argomenti approfonditi riguardano: progetto e realizzazione di bobine Helmholtz, sviluppo di sensori magnetici ad induzione, integrazione di sensori AMR in sistemi di localizzazione tridimensionale.ope

    Magnetotelluric study in the Moine Thrust region of Northern Scotland

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