A. James Clark School of Engineering

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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.

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Subject: search.filters.subject.linearization

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    LINEARIZED OPTICALLY PHASE-MODULATED FIBER OPTIC LINKS FOR MICROWAVE SIGNAL TRANSPORT
    (2009) Haas, Bryan Michael; Murphy, Thomas E; Electrical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Several novel phase-modulated fiber optic links for analog or microwave signal transport up to at least 20 GHz frequency are theoretically developed and experimentally demonstrated. Each link uses a linearization technique exploiting the Lithium Niobate modulator's electro-optic anisotropy between orthogonal crystallographic axes that has not previously been applied to phase-modulated links. This technique and its variants suppress the dominant third-order distortion product to extend the sub-octave spur-free dynamic range of the systems, and does so passively using the modulator instead of with processing at the receiver. Two of the links incorporate frequency downconversion, with one of them employing a new method to spectrally filter the local oscillator and signal sidebands together. This both downconverts the signal to an appropriate intermediate frequency and causes the phase modulation to appear as intensity modulation for photodetection with a low-speed detector. This technique does not require a separate optical oscillator source and can be implemented with commercial hardware.
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    The generalized Sundman transformation for propagation of high-eccentricity elliptical orbits
    (Univelt, Inc., 2002-01) Berry, Matthew M.; Healy, Liam M.
    A generalized Sundman transformation dt = cr^n ds for exponent n >= 1 may be used to accelerate the numerical computation of high-eccentricity orbits, by transforming time t to a new independent variable s. Once transformed, the integration in uniform steps of s effectively gives analytic step variation in t with larger time steps at apogee than at perigee, making errors at each point roughly comparable. In this paper, we develop techniques for assessing accuracy of s-integration in the presence of perturbations, and analyze the effectiveness of regularizing the transformed equations. A computational speed comparison is provided.
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    System Modeling and Controller Design for a Single Degree of Freedom Spacecraft Simulator
    (2005-05-03) Vess, Melissa Elaine Fleck; Sanner, Robert M; Aerospace Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Control systems theory is an important field of study for many branches of engineering. Teaching control systems to engineering students, however, is often difficult due to the abstract nature of the subject. TableSat is a single degree of freedom spacecraft simulator that includes sensors, actuators, a power system, and a flight processor. Students can use TableSat to design and test controllers, allowing them to see how theoretically designed controllers function in a real system. TableSat, like all real systems, is highly nonlinear. To make TableSat an effective teaching tool, the system nonlinearities are identified and compensation methods undertaken to eliminate those nonlinearities. Linear and truth system models are created for use in controller design and testing. The system models are tested and verified and then used to design and test several controllers and estimators. Results are presented that compare results for the linear model, truth model, and real TableSat system.