by Terry Kin-chung Lo. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1994. / Includes bibliographical references (leaf 128). / Dedication --- p.i / Acknowledgements --- p.ii / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Outline of Thesis --- p.1 / Chapter 1.2 --- Microstrip to Slotline Transition --- p.3 / Chapter 1.3 --- Finite Difference as a Numerical Method --- p.4 / Chapter Chapter 2 --- The Method of Finite Difference in Time Domain / Chapter 2.1 --- An Introduction and Brief History --- p.1 / Chapter 2.2 --- The Methodology of FDTD --- p.11 / Chapter 2.3 --- The Yee's Algorithm --- p.13 / Chapter 2.4 --- Stability Criterion --- p.19 / Chapter 2.5 --- Interfaces Between Media --- p.21 / Chapter 2.6 --- Lattice Truncation Condition --- p.24 / Chapter 2.7 --- Error Analysis --- p.28 / Chapter 2.8 --- Implementation of Programs --- p.33 / Chapter 2.9 --- Summary --- p.35 / Chapter Chapter 3 --- Absorbing Boundary Conditions / Chapter 3.1 --- Introduction --- p.39 / Chapter 3.2 --- Mur's ABC --- p.40 / Chapter 3.3 --- Liao's ABC --- p.42 / Chapter 3.4 --- Dispersive ABC --- p.45 / Chapter 3.5 --- Comparison between Mur's ABC & Liao's ABC --- p.47 / Chapter 3.6 --- "Comparison among Mur's 1st Order ABC, Liao's ABC & DBC" --- p.51 / Chapter 3.7 --- Summary --- p.55 / Chapter Chapter 4 --- Microstrip-Slotline Transitions / Chapter 4.1 --- Introduction --- p.57 / Chapter 4.2 --- Approach --- p.59 / Chapter 4.3 --- Single Quarter-Wave Microstrip-Slotline Transitions --- p.67 / Chapter 4.4 --- Single Y-Strip-Slotline Transitions --- p.78 / Chapter 4.5 --- Shorted-Stub Y-Strip-Slotline Transitions --- p.88 / Chapter 4.6 --- Y-Strip-180°-Slotline Transitions --- p.96 / Chapter 4.7 --- Y-Strip-Y-Slot Transitions --- p.104 / Chapter 4.8 --- Y-Strip-Open-Stub-Y-Slot Transitions --- p.112 / Chapter 4.9 --- YY-Transitions --- p.120 / Chapter 4.10 --- Summary --- p.127 / Chapter Chapter 5 --- Conclusions & Future Development / Chapter 5.1 --- Conclusions --- p.129 / Chapter 5.2 --- Future Development --- p.131 / Appendix / Fortran 77 Code of Single Quarter-Wave Microstrip-Slotline Transition --- p.132

No description available.

by Tam Wai Yip. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1990. / Bibliography: leaves [124]-[127] / ACKNOWLEDGEMENT --- p.i / LIST OF SYMBOLS --- p.ii / Chapter CHAPTER 1 --- INTRODUCTION --- p.1-1 / Chapter CHAPTER 2 --- ANALYSIS OF MICROSTRIP ANTENNA ON A PLANAR SURFACE --- p.2-1 / Chapter 2.1 --- Dyadic Green's function formulation of a double-patch system --- p.2-3 / Chapter 2.1.1 --- Field components --- p.2-4 / Chapter 2.1.2 --- Boundary conditions and dyadic Green's function --- p.2-8 / Chapter 2.2 --- Microstrip antenna with an airgap --- p.2-14 / Chapter 2.3 --- Microstrip antenna with a superstate --- p.2-16 / Chapter 2.4 --- Galerkin's method --- p.2-18 / Chapter 2.5 --- Numerical computation --- p.2-25 / Chapter 2.6 --- Results and discussions --- p.2-30 / Chapter CHAPTER 3 --- ANALYSIS OF MICROSTRIP ANTENNA ON SPHERICAL SURFACE --- p.3-1 / Chapter 3.1 --- Fields in spherical coordinates --- p.3-3 / Chapter 3.1.1 --- solution of scalar Helmholtz equation in spherical coordinates --- p.3-3 / Chapter 3.1.2 --- Vector potentials --- p.3-6 / Chapter 3.2 --- Cavity model approach --- p.3-10 / Chapter 3.2.1 --- Formulation of radiation patterns --- p.3-11 / Chapter 3.2.2 --- Results and discussions --- p.3-23 / Chapter 3.3 --- Spectral domain approach --- p.3-39 / Chapter 3.3.1 --- General formulation --- p.3-39 / Chapter 3.3.2 --- Complex resonant frequency --- p.3-48 / Chapter 3.3.3 --- Far field radiation pattern --- p.3-51 / Chapter 3.3.4 --- Current distribution --- p.3-52 / Chapter 3.3.5 --- Limiting case of thin dielectric --- p.3-58 / Chapter 3.3.6 --- Results and discussions --- p.3-63 / Chapter CHAPTER 4 --- CONCLUSIONS --- p.4-1 / REFERENCES / Chapter APPENDIX I --- ASSOCIATED LEGENDRE FUNCTIONS / Chapter APPENDIX II --- SPHERICAL BESSEL FUNCTIONS / Chapter APPENDIX III --- VECTOR LEGENDRE SERIES / Chapter APPENDIX IV --- RESONANT FREQUENCY RELATION FOR THIN DIELECTRIC / Chapter APPENDIX V --- LIST OF PUBLICATIONS THAT ARE PRODUCED BY THE STUDIES

The design and characterization of both electromagnetic bandgap (EBG) and inter-coupled split-ring resonator (SRR) structures utilized in microwave frequencies were proposed and studied. A new double-stopband EBG structure with a passband region of 14 to 18 GHz was initially constructed by determining the critical structural ratios. To reduce the size of EBG structure, a novel tapered array pattern was introduced. The structural period, the number of slot, and the length of slot were examined and a strong correlation was found between the lowpass cutoff frequency and the center slot length. Non-linearly tapered configuration was applied to enhance the filter performance and its size was only 57% of the conventional EBG structure. Inter-coupled SRR was also examined and utilized as a bandpass filter when it is implemented on the microstrip line for the first time. It was found that the proposed structure can provide a fractional bandwidth of over 68% with an insertion loss of 0.81 dB in the passband region with a device size of 15.5 mm. / Chemical bath deposited Cadmium Sulfide (CdS) thin film was applied to the microwave structures to construct switchable filters. The illumination-sensitive CdS thin film's sheet resistance has been demonstrated to be able to switch from 300 to 109 O/square. With the proposed "conductive-islands" implementation, switching of EBG structure's transmission coefficient (S21) was achieved from 31.3 dB to 5.6 dB at 13 GHz. The inter-coupled SRR structure also showed a S21 switching response from 19 dB to 1.5 dB at 5 GHz. Therefore, optically controlled microwave filters were successfully constructed and realized. / Critical contributions in the field of microwave periodic structures are the characterization and the construction of double-stopband structure, linearly and non-linearly tapered array structures, and inter-coupled SRR structures. Vital characteristics and advantages discovered include wide stopband, reduced size, and large fractional bandwidth. Chemical bath deposited CdS thin films were studied to achieve an ultra low sheet resistance and high photosensitivity. Important applications associated with these structures are microwave lowpass/bandpass filters and optically controlled filters.

Thesis (M.S.)--Wisconsin. / Includes bibliographical references (leaves 52-53).

Thesis (Ph. D.)--Lehigh University, 2006. / Includes vita. Includes bibliographical references (leaves 115-127).

No description available.

RF/microwave terrestrial point-to-point and satellite communication systems employ a large number of waveguide components operating at microwave and millimeter wave frequencies. Accurate design of these components for optimum performance of the overall system is critical. To achieve this, computationally efficient and accurate numerical methods are indispensable tools in the design and optimization of components and subsystems. Among the large variety of potentially suitable numerical methods, the mode matching method in conjunction with the generalized scattering matrix technique has been found to be one of the most reliable and straightforward techniques to design waveguide components. In the past the method has been mainly applied to eigenvalue and scattering problems in rectangular waveguides. In this thesis, the mode matching method is extended to ridge waveguide problems in circular waveguides and thus closes a gap in the literature that has existed for a long time. The thesis begins with a study of the basic principles of the mode matching method as it is known from rectangular waveguides. These principles are then applied to the analysis of the rectangular ridged and coaxial waveguide, followed by an eigenvalue analysis of ridged circular waveguide. Rather than rectangular ridges, ridges of uniform angular thickness (conically shaped) are used in the circular waveguide to avoid a mixed coordinate system which would render the mode matching method computationally very inefficient. On the other hand, conically shaped ridges are as easy to fabricate as rectangular ridges and are not detrimental to the electrical performance of the component. The thesis then continues to treat the discontinuity problem at the interface between the empty circular waveguide and ridged circular waveguide. To verify the computed scattering parameters, measurements were performed and good agreement was found. By cascading several discontinuities transformers and evanescent mode filters were designed. A fifth order filter was designed and fabricated and also here good agreement between measured and computed data was found. The final chapter in the thesis analyses the coupling between orthogonal modes in the presence of an asymmetric discontinuity. Determining the coupling factor between orthogonal modes is an integral part of the design of polarizers and dual mode filters and for conically shaped ridges, has not been published in the open literature yet. To realize various coupling coefficients, a single or double ridges must be placed at an arbitrary angle to the exciting wave. The mode matching method is extended to include also this case and various convergence tests have been performed to validate the algorithm . As a final example, the algorithm has been applied to design a circular polarizer with two ridges. Although only two-port problems are treated in this thesis, the basic framework for the mode matching method in circular waveguide has been established and can now be extended to three-port problems. This will be the subject of future work to analyze and design power dividers and orthomode transducers. / Graduate

This research is devoted to an investigation on the attractive width of high voltage transmission lines to lightning strikes. In order to design the optimal lightning protection, the estimated number of lightning flashes on the line, which is based on its attractive width, needs to be determined. The investigation was performed using experiments with model tests at the Mississippi State University High Voltage Laboratory. For laboratory experiments, a total of 2,100 negative and positive switching impulse voltages were applied to transmission line models from a conducting rod, which represented a lightning downward leader. Different tested models of transmission lines on a scale of 1:100 were used. The effects of overhead ground wires, phase conductors, tower structures, and the magnitude and polarity of lightning strokes were also studied. The attractive width increased gradually with the height of overhead ground wires and towers as well as the magnitude of the lightning stroke current. Impulse polarity had an impact on the attractive width, and the attractive width for negative polarity was larger than that for positive polarity. The taller tower had more effect on flash distribution to transmission lines than the shorter one. The experimental results agree with the actual transmission line observations published in literature. The new expressions for the attractive width of transmission lines, based on the experimental results, were established. The accurate estimation of the attractive width can help electric power utilities plan transmission systems reliably and economically. The detailed description of the background problem, proposed method, experimental results, and analysis are presented in this dissertation.

No description available.