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).

No description available.

No description available.

published_or_final_version / Electrical Engineering / Doctoral / Doctor of Philosophy

Coplanar microstrip structures placed on dielectric substrates are used as high frequency electro-optic modulators. The method of lines, a mathematical technique for solving partial differential equations, has been applied to solve for the propagation characteristics of such a configuration. It has been determined that simple transmission line models are adequate to describe this system. The propagation characteristics are expressed in terms of the equivalent impedance and the phase velocity of the signal on the microstrip. In order to maximize the effective bandwidth of the modulator, the impedance is matched to that of the surrounding dielectric substrate, and the difference in the phase velocities of the two signals is minimized. The numerical technique developed here allows for the analysis of inhomogeneous dielectric substrates, so that trench structures for tuning the propagation characteristics to their desired values can be modelled. The numerical results for typical structures are presented, and suggest that the method of lines is a viable one for analyzing these modulator structures. / Graduation date: 1991

In this thesis a numerical technique to model general microstrip asymmetric and multiple step discontinuities is presented. The method is based on a magnetic wall waveguide model that is assumed to be valid for describing the electromagnetic fields associated with the microstrip line and in the vicinity of microstrip discontinuities. The fields are expanded in the uniform regions and the mode-matching method is applied at the discontinuities to analyze for the frequency dependent transmission properties of the multi ports. The generalized scattering matrix technique is used to model cascaded interacting discontinuities and is used to compute the properties of double-step and multi port structures. The generalized scattering matrix formulation takes into account the scattering phenomena of the dominant and all of the higher-order modes including evanescent ones. The validity of this model has been discussed extensively, and it is shown that the model can be used to describe the microstrip discontinuities with acceptable accuracy. The technique is applied (1) to study the transmission characteristics of asymmetric step discontinuities; (2) to design a filter for a desired frequency range using interacting asymmetric double step micros trip line; and (3) to design a new nominal 3db power devider of large bandwidth consisting of a three port rectangular patch. The techniques and models presented can be used in computer-aided analysis and design of such circuits. / Graduation date: 1993

Thesis (M.S. in Systems Engineering (Electronic Warfare))--Naval Postgraduate School, September 1990. / Thesis Advisor(s): Atwater, Harry A. Second Reader: Janaswamy, Rama. "September 1990." Description based on title screen as viewed on December 29, 2009. DTIC Identifier(s): Suspended striplines, microstrip lines, equivalent circuits, program listings, theses. Author(s) subject terms: Suspended-microstrip line, step discontinuity, equivalent circuit model, step-change. Includes bibliographical references (p. 60). Also available in print.

Thesis (M.Phil.)--City University of Hong Kong, 2009. / "Submitted to Department of Electronic Engineering in partial fulfillment of the requirements for the degree of Master of Philosophy." Includes bibliographical references.