Analysis and applications of reconfigurable antennas and novel periodic structures

A new type of antenna called the “reconfigurable” antenna, which serves multiple functions over different frequency bands and greatly reduces the weight, size and cost of antenna platforms is presented. The proposed structure is a combination of microstrip-based leaky-mode antennas and several patch antennas operating at different frequencies. The feasibility of the reconfigurable antenna is demonstrated by using PIN diode switches to control different radiation configurations.; A low loss slow-wave structure is numerically and experimentally investigated. The structure is based on a microstrip line on UC-PBG ground plane. Dependency of the slow-wave factor on lattice dimensions is investigated. The slow-wave factor has also been simulated by the FDTD method to provide numerical verification of the accuracy of the results. Numerical results reveal that the slow-wave microstrip structure can achieve small attenuation per wavelength.; Strong forward coupling and slow-wave effects between two parallel microstrip lines on UC-PBG ground plane are observed, even though the two lines are separated by very large gap spacing. The even- and odd-mode effective dielectric constants have been calculated using the FDTD method to investigate this phenomenon. The slow-wave effects and enhanced coupling will help in the design of forward-wave directional couplers with reduced line lengths and relaxed gap spacing requirements.; A microstrip structure with perforated ground plane including slot resonators is studied. The single isolated slot resonator is very compact and exhibits well-characterized field distributions at its resonant frequencies. The knowledge of these field distributions is exploited to derive equivalent RLC networks for the first two resonances, with parameters extracted from full-wave simulations. The resulting lumped-element model is extended to a cascade of multiple slots under the condition that the resonators are weakly coupled. When the resonators are spaced closely enough as to present strong mutual coupling, periodic boundary conditions are used to compute the exact dispersion relation to determine passband and stopband frequency ranges for the structure.; Left-handed materials are defined to be the materials with both negative permittivity and permeability. To obtain certain macroscopic electromagnetic characteristics we propose a simulation technique for LHMs using an effective medium approach. Some interesting features such as anti-parallel propagation between the wave vector and Poynting vector, boundary conditions at the RH/LH interface, and reversal of Snell's law of refraction will be analyzed and demonstrated using a rectangular waveguide loaded with a LHM.