Problems in the demodulation of one, two, and three-dimensional signals are investigated. In one-dimensional linear systems the analytic signal and the Hilbert transform are central to the understanding of both modulation and demodulation. However, it is shown that an efficient nonlinear algorithm exists which is not explicable purely in terms of an approximation to the Hilbert transform. The algorithm is applied to the problem of finding the envelope peak of a white light interferogram. The accuracy of peak location is then shown to compare favourably with conventional, but less efficient, techniques. In two dimensions (2-D) the intensity of a wavefield yields to a phase demodulation technique equivalent to direct phase retrieval. The special symmetry of a Helmholtz wavefield allows a unique inversion of an autocorrelation. More generally, a 2-D (non-Helmholtz) fringe pattern can be demodulated by an isotropic 2-D extension of the Hilbert transform that uses a spiral phase signum function. The range of validity of the new transform is established using the asymptotic method of stationary phase. Simulations of the algorithm confirm that deviations from the ideal occur where the fringe pattern curvature is larger than the fringe frequency. A new self-calibrating algorithm for arbitrary sequences of phase-shifted interferograms is developed using the aforementioned spiral phase transform. The algorithm is shown to work even with discontinuous fringe patterns, which are known to seriously hamper other methods. Initial simulations of the algorithm indicate an accuracy of 5 milliradians is achievable. Previously undocumented connections between the demodulation techniques are uncovered and discussed.

Thesis (M.S.)--Auburn University, 2007. / Abstract. Vita. Includes bibliographic references (ℓ. 48-50)

Thesis (Ph. D.)--University of Hong Kong, 2008. / Also available in print.

Thesis (M. App. Sc.)--Carleton University, 2001. / Includes bibliographical references (p. 54-56). Also available in electronic format on the Internet.

Zugl.: München, Techn. Univ., Diss., 2008

Thesis (doctoral)--Technische Universiteit Delft, 1998. / Includes bibliographical references.

Thesis (doctoral)--Technische Universiteit Delft, 1998. / Includes bibliographical references.

Thesis (M. Eng.), Memorial University of Newfoundland, 1999. / Bibliography: p. 129-138.

Thesis (MEng)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The purpose of this thesis is the description of the development of a QPSK demodulator for the Sunsat 1 groundstation. A general overview of the functioning and requirements of a typical QPSK demodulator system is given. Several methods or algorithms for clock and carrier recovery are discussed. Specific attention is given to the QPSK demodulator chipset from Philips used for the implementation of the demodulator. The digital decoding logic used to serialize the parallel I and Q datastream is explained. Finally measurement techniques for performance evaluation of QPSK systems are investigated. As part of this the implementation loss of the developed QPSK demodulator is measured. / AFRIKAANSE OPSOMMING: Die doelwit van hierdie tesis is om die ontwikkeling van 'n QPSK demodulator vir die Sunsat 1 grondstasie te beskryf. 'n Algemene oorsig oor die funksionering en vereistes van 'n tipiese QPSK demodulator stelsel word gegee. Verskeie algoritmes en tegnieke vir klok en draersein herwinning word ondersoek en bespreek. Spesifieke verwysing word telkens gemaak na die QPSK demodulasie vlokkie paar van Philips gebruik vir die implementering van die demodulator. Die digitale dekodering logika benodig vir die datastroom verpakking word ondersoek en beskryf. Laastens word daar gekyk na meettegnieke en evaluasie van QPSK demodulasie stelsels se prestasie. As deel hiervan word die implementasie verlies van die ontwikkelde QPSK demodulator stelsel gemeet.

This thesis presents packet-level channel modeling, spectrum efficiency optimization and channel estimation for wireless cooperative communication systems with diversity combining. Cooperative transmission in a wireless network allows neighboring nodes to share their communication resources to create a virtual antenna array by distributed transmission and signal processing, which is useful to exploit spatial diversity, increase channel capacity, and attain wider service coverage with single-antenna terminals. How to exploit spatial diversity and leverage the multi-hop channel structure is an important research issue for the cooperative network. In this thesis, two cooperative schemes are considered, amplify and forward (AF) and demodulation and forward (DMF). For AF cooperative systems, finite state Markov chain (FSMC) models are designed in analyzing the system performance considering time-varying channel behaviors and facilitating fast channel simulation. For DMF cooperative systems, first we formulate the optimization problem that jointly chooses the modulation schemes at the source and relay nodes, to maximize the throughput of cooperative systems under the BER constraint. Second, we propose to use the soft values of each bit to devise a simple and effective combining scheme, which can be applied for both AF and DMF cooperative systems. Third, as the soft values from demodulation process can also be used for measuring the channel estimation accuracy, a soft value-assisted channel estimation has been proposed by iteratively utilizing soft values to refine the accurate channel estimation. In addition, we also implement the soft value module in OFDM-based transceiver system based on a GNU Radio/USRP2 platform, and verify the effectiveness and performance improvement for the proposed SVC systems. As considering wireless cooperative systems has attracted increasing attentions from both academic and industry to meet the demanding of the high data rate transmission, the packet-level channel modeling, adaptive modulation, spectrum efficiency improvement frameworks based on soft value combining and accurate channel estimation algorithms proposed in this thesis are essential for future proliferation of high data rate, reliable and efficient wireless communication networks. / Graduate / 0537 / 0544 / 0984