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Call number: LD2668 .T4 1963 J67 / Master of Science

The worldwide demand for personal communication system (PCS) devices is motivating the development of compact, high-performance antennas. It is also prompting a better understanding of the effects of the user and the mobile communication environment on the antenna performance. The objective of this dissertation is to add to the current knowledge in both areas. Using the Finite-Difference Time-Domain (FDTD) technique, a monopole antenna and a diversity antenna were modeled for PCS applications. Also, techniques were developed and applied to facilitate the accurate numerical analysis of PCS antennas and to investigate the electromagnetic interaction between PCS antennas and the mobile communication environment. A monopole antenna and a polarization diversity antenna (PDA) were investigated at frequencies near 900 MHz. Antenna performance was evaluated in terms of the far-field radiation patterns, the mean effective gain (MEG), the radiation efficiency and the specific absorption rate (SAR) of energy in the user's body. For the diversity antenna, the statistical independence of the two diversity branches was determined from the correlation coefficient. The antenna modeling incorporated the antenna, a cellular telephone handset, models of the user's head and hand, and a statistical model of the mobile environment. Two mobile environments, an urban outdoor environment and a suburban outdoor environment, were modeled. The results show that (i) changing the antenna configuration from the monopole antenna to the PDA significantly affects the antenna efficiency and SAR in the user’s body; (ii) the type of mobile communication environment chosen (urban or suburban) has a pronounced effect on the correlation coefficient of the PDA and on the MEGs of the PDA and the monopole antenna; (iii) in terms of the MEG, the PDA is more sensitive than the monopole antenna to the presence of the user’s body; and (iv) overall, the PDA performs better than the monopole antenna in terms of antenna efficiency, peak averaged SAR in the head, and MEG. The accurate FDTD modeling of wires is crucial to the FDTD analysis of PCS antennas, particularly as monopole antennas and other linear wire antennas are often used with PCS devices. A study of the FDTD modeling of thin wires is included in this dissertation. The accuracy of the wire models was determined by calculating the input impedance of a dipole antenna over a broad range of dipole radii and comparing with the results of a Method of Moments formulation. Two existing thin wire models were analyzed and found to be inaccurate for some purposes. This finding led to the development of a new model, which includes a special treatment of the field components at the wire ends and a model of the source region. The proposed wire model is more accurate than the two existing wire models for a given spatial resolution. Thus, this new wire model facilitates accurate computations of input impedance and resonant frequency for linear wire antennas. The stability of the wire model was addressed, and a formulation for the maximum stability coefficient to be used with the proposed thin wire model was developed. / Graduate

Thesis (Ph. D.)--University of Queensland, 2001. / Includes bibliographical references.

Thesis (Ph. D.)--Lehigh University, 2001. / Includes vita. Includes bibliographical references (leaves 106-114).

published_or_final_version / abstract / toc / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

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