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Anomalous perturbations of the ionosphere have been observed either as uctuations in the critical frequency of the F-region ionosphere, foF2, or as uctuations in the nighttime VLF signals that propagate through the Earth Ionosphere Waveguide. All anomalies appear from an earliest of three weeks to one day prior to an earthquake occurrence, hence leading to be used as possible presursors and aid in short term earthquake prediction. Earthquakes of magnitude 5.5 and greater have a signi cant chance of having associated ionospheric anomalies, and anomalies are only detected within a radius of 500km from the epicentre. Solar events, however, greatly a ect the ionosphere and make seismogenic ionospheric signals di cult to isolate. This study concentrates on anomalous VLF signal perturbations observed along the propagation path between the NWC transmitter in Australia and narrowband receivers in Budapest and Tihany, Hungary for July 2007 to February 2008. Comparisons of anomaly appearances and seismic activity occurring within the Dobrovolsky area to the propagation path were carried out, with anomalies being observed predominantly prior to major seismic events. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2013.

Ultra-wideband (UWB) wireless systems rely on signals spanning very wide bandwidths, typically several gigahertz, for information transmission. The distinguishing feature of UWB communications technology is the unrivalled data-rates it provides, with other benefits such as fade resistance and spectral reusability. These characteristics render UWB the technology of choice for a gamut of modern wireless communications applications, including multimedia transmission, personal- and body-area networks, imaging devices, and sensor networks. The use of wide bandwidth signals, however, leads to many complications that necessitate specialised design considerations. The propagation channel and system components acquire frequency-selective characteristics, and their nonlinear and dispersive nature, usually innocuous in a conventional setting, causes signal distortion and erroneous detection. This thesis analyses various aspects of the indoor channel and the distortion to a UWB signal propagating through it. The performance of transmitter and receiver sub-systems is evaluated, with an emphasis on the challenges posed by the large operating bandwidth. The significance of incorporating this knowledge into the system design process is demonstrated, and a novel framework for optimising the performance-complexity tradeoff is presented. • The following are the contributions of this thesis to the state of the art in UWB communications. • Experimental characterisation of the indoor UWB channel spanning the FCC band (3.1-10.6 GHz) • Demonstration of the variability of propagation characteristics in the spectral sub-bands • Assessment of frequency-dependent pathless and the consequent signal waveform distortion • Polarimetric analysis of the temporal, spectral and angular channel evolution • Evaluation of rake receiver performance and its dependence on various channel conditions • Investigation of the effect of antenna angular-spectral distortion on signal propagation • A technique for the normalisation of UWB link aberration due to antennas • Performance evaluation of diversity and spatial multiplexing with multiple-antenna systems • Design of gigabit wireless links for high data-rate applications or high user density scenarios • A novel holistic framework for the design of an optimal UWB communications system.

Thesis (M.S.)--University of Hawaii at Manoa, 2005. / Includes bibliographical references. / vi, 62 leaves, bound ill. 29 cm

v, 137 p. : ill., plates ; 26 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Physics, 1974

Thesis (Ph.D.) -- University of Adelaide, Dept. of Physics, 1974.

Thesis (Ph. D.)--Ohio University, August, 1999. / Title from PDF t.p.

Thesis (M.Sc.)--University of Adelaide, Dept. of Physics, 1969. / Candidate's reply (16 leaves) in pocket.