Predicting performance metrics for the next-generation of multi-mode and multi-antenna wireless communication systems demands site-specific knowledge of the wireless channel's underlying radio wave propagation mechanisms. This thesis describes the first measurement system capable of characterizing individual propagation mechanisms in situ. The measurement system merges a high-resolution spatio-temporal wireless channel sounder with a new field reconstruction technique to provide complete knowledge of the wireless channel's impulse response throughout a 2-dimensional region. This wealth of data may be combined with space-time filtering techniques to isolate and characterize individual propagation mechanisms. The utility of the spatio-temporal measurement system is demonstrated through a measurement-based investigation of diffraction around building corners. These measurements are combined with space-time filtering techniques and a new linear wedge diffraction model to extract the first semi-mpirical diffraction coefficient. Specific contributions of this thesis are: * The first ultra-wideband single-input multiple-output (SIMO) channel sounder based upon the sliding correlator architecture. * A quasi 2-dimensional field reconstruction technique based upon a conjoint cylindrical wave expansion of coherent perimeter measurements. * A wireless channel ``filming' technique that records the time-domain evolution of the wireless channel throughout a 2-dimensional region. * High-resolution measurements of the space-time wireless channel near a right-angled brick building corner. * The application of space-time filtering techniques to isolate the edge diffraction problem from the overall wireless channel. * An approximate uniform geometrical theory of diffraction (UTD)-style linear model describing diffraction by an impedance wedge. * The first-ever semi-empirical diffraction coefficient extracted from in situ measurement data. This thesis paves the way for several new avenues of research. The comprehensive measurement data provided by channel "filming" will enable researchers to develop and implement powerful space-time filtering techniques that facilitate measurement-based investigations of radio wave propagation. The measurement procedure described in this thesis may be adapted to extract realistic reflection and rough-surface scattering coefficients. Finally, exhaustive measurements of individual propagation mechanisms will enable the first semi-empirical propagation model that integrates empirical descriptions of propagation mechanisms into a UTD-style mechanistic framework.

M. Tech. Electrical Engineering. / Produces findings, based on scientific methods, to verify or refute electromagnetic propagation, generated with Synthetic Poynting Vector formation, that will enable small but efficient electrical antennas.

Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008. / Committee Chair: Manos M. Tentzeris; Committee Co-Chair: John Papapolymerou; Committee Member: Andrew F. Peterson; Committee Member: Chang-Ho Lee; Committee Member: John D. Cressler; Committee Member: Joy Laskar.

Thesis (M.Eng.)--Memorial University of Newfoundland, 1999. / Bibliography: leaves [97]-101.

Thesis (M.S.E.E.)--University of Puerto Rico, Mayagüez Campus, 2005. / Tables. Printout. Includes bibliographical references (leaves146-148).

A method to synthesize the sound radiation characteristics of musical instruments in a wave field synthesis (WFS) system is proposed and tested. Radiation patterns of a violin are measured with a circular microphone array which consists of 128 pressure receivers. For each critical frequency band one exemplary radiation pattern is decomposed to circular harmonics of order 0 to 64. So the radiation characteristic of the violin is represented by 25 complex radiation patterns. On the reproduction side, these circular harmonics are approximated by 128 densely spaced monopoles by means of 128 broadband impulses. An anechoic violin recording is convolved with these impulses, yielding 128 filtered versions of the recording. These are then synthesized as 128 monopole sources in a WFS system and compared to a virtual monopole playing the unfiltered recording. The study participants perceive the tone color of the recreated virtual violin as being dependent on the listening position and report that the two source types have a different ‘presence’. The test persons rate the virtual violin as less natural, sometimes remarking that the filtering is audible at high frequencies. Further studies with a denser spacing of the virtual monopoles and a presentation in an anechoic room are planned.

A novel microstrip patch antenna topology is presented for achieving a dual-band response with arbitrarily closely spaced resonances. This topology is based on a coupled transmission line structure in order to take advantage of the separation in propagation constants for parallel (even-mode) and anti-parallel (odd-mode) current modes. Applying a metamaterials inspired design approach, periodic reactive load­ings are used to design the underlying transmission line to have specific propagation constants necessary to realize a desired separation between two resonant frequencies. Using a single probe feed for a finite coupled line segment, both even-and odd-mode resonances can be excited to radiate efficiently at their respective design frequencies. The efficiency of the odd-mode radiation is enhanced by separating the two lines, while strong coupling is maintained by inserting a series of narrowly-separated thin loops between them. Several example resonant antenna designs, in the 2.45 GHz band, are presented. The directivities of these microstrip patch antennas are enhanced by optimizing the physical length of the resonant structure. For a resonant antenna obtained by cas­cading several unit cells of reactively loaded microstrip segments, dispersion analysis is employed for the unit-cell design. Maximum directivity is achieved by choosing the overall physical length to be slightly less than a half wavelength in free space at the design frequency. This gain optimization is applied to three coupled-line antennas, as well as a single resonance patch. Excellent agreement is observed between simulated and measured responses across all designs. The potential of loading the coupled line structure with active components is also explored. Varactor diodes are placed on coupled-line structures in two configurations. In one configuration, both resonant frequencies are affected. In the other configura­tion, only the odd-mode characteristics are reconfigured. In this way, the resonant frequency of either one or both modes can be adjusted by applying a DC bias voltage to the varactor diode loading elements. Two antennas, one employing each of these topologies, were designed and fabricated. Control of the resonant frequency over the predicted range through applying a bias voltage is observed with the fabricated prototypes.

No / Noise amplitude distribution measurements relevant to%satellite-mobile radio systems are reported. The rationale for the%measurements is outlined and the choice of measurement parameters%justified. The measurement equipment and measurement methodology are%described in detail. Results characterizing the elevation angle%distribution of impulsive noise are presented for rural, suburban and%urban environments and also for an arterial road (U.K. motorway)%carrying high density, fast moving traffic. Measurements of the levels%of impulsive noise to be expected in each environment for high- and%low-elevation satellite scenarios using appropriate antenna%configurations are also presented

The objective of this research is to realize compact and reconfigurable antennas for next generation Ultra Wide Band (UWB) and Wireless Local Area Network (WLAN) applications. The contributions of this research are, a methodology for designing compact UWB antennas, a compact WLAN prototype antenna with reconfigurable characteristics in both radiation pattern and frequency of operation, and compact UWB antennas with reconfigurable WLAN band rejection characteristics. For the completion of this dissertation, five research projects have been studied. First, a double exponentially tapered slot antenna with conformal shape, high gain, and consistent radiation patterns is implemented. The radiation pattern consistency results in minimum distortion for any transmitted pulse. The second and third projects involve an elliptical slot with a tuning uneven U-shaped stub and two cactus-shaped monopoles. The elliptical slot demonstrates omni-directional radiation patterns and compact size. As an improved iteration of the elliptical slot antenna, two cactus-shaped monopoles are implemented. The two prototypes occupy only 60% and 40%, respectively, of the area that the original elliptical slot occupies resulting in a significant size reduction, while maintaining omni-directional radiation patterns. Through the cactus-shaped monopoles some general design methodologies for UWB antennas are introduced and successfully applied. The fourth research topic introduced, concerns the study of compact elliptical UWB monopoles. Several prototypes of different geometrical characteristics were designed and tested. Broadband matching techniques and the integration of reconfigurable features on the elliptical radiator are investigated. For the reconfigurable UWB antenna, resonating elements are used to create a rejection band in the frequency range that is occupied by WLAN applications. The performance of several of the introduced slot and monopole antennas are tested when the antennas under detection are mounted and operate on non-planar surfaces. Finally, a reconfigurable annular slot antenna operating at the wireless local area network (WLAN) band is implemented. The proposed antenna demonstrates reconfigurable characteristics in both radiation pattern and return loss. All of the UWB antennas are fabricated on liquid crystal polymer (LCP) and can be easily integrated with active components on the same module using system on package (SoP) technology.

M. Tech. Electrical Engineering. / Objectives of this research is to use the node orientation, coupled with antenna radiation pattern of each node, to improve the Received Signal Strength (RSS) range measurement technique. As energy eciency is critical to WSNs, it is necessary to minimize both computation and communication costs in any operation involving WSNs,including during the localisation process. To achieve that, accelerometer measurements are used to reduce the number of iteration of the optimisation process during the refinement phase by computing more accurately an initial position for the optimisation using dead reckoning and approach the localisation in a distributed manner. The contribution of this is the investigation and development of an ecient localisation algorithm that can be used on a low cost wireless sensor board developed using existing technology. A review of the existing methods is conducted to highlight the key aspect to consider when developing an ecient localisation algorithms. A mathematical modelling of the proposed algorithm is developed and simulation is conducted to analyse the performance of the algorithm. An exhaustive test bed hardware has been designed on which the algorithm can to be validated.