Leakage Characteristics Of Periodic Waveguides Based On GSM Method

The dissertation mainly studies the substrate integrated waveguide(SIW), THz leaky-mode synthetic transmission line and composite right/left-handed transmission line(CRLH-TL). The dissertation presents the hybrid generalized scattering matrix based on the finite element method(GSM/FEM) written in Mathematica, with the periodic Bloch-Floquet boundary and the perfectly matched layer(PML). This method accurately calculates the complex propagation constants of the periodical SIW describing the electromagnetic fields surrounding the microstrip section(or parallel plate section) of the SIW, depicts the fields inside and outside the ideal rectangular waveguide walls, establishes a rigorous formulation to tackle the periodic guided wave structures with results validated by experiments.Using the GSM/FEM method to solve the complex propagation constants, the dissertation begins with the investigation of the surface-wave leakage phenomenon that was either negligently ignored or attributed to numerical and/or experimental instability in the past twenty years years since the SIW was introduced. The dissertation investigates both PCB(printed circuit board) SIW and CMOS SIW structures with the aid of ANSYS software HFSSTM, which is integrated to a master code based on the GSM/FEM formulation reported in the dissertation. Furthermore, three-dimensional electromagnetic field analyses implemented to validate the leakage phenomenon from a substrate integrated waveguide(SIW) on a grounded dielectric substrate, which propagates the TM0 mode at the lowest order. On measurement validation, we conducted two steps. The first step was to verify the extracted results using the proposed hybrid GSM/FEM formulation method against the measured data in classical literatures. Next, the dissertation compares the measured CMOS SIW data against the theoretical results. The dissertation reports two substrate integrated waveguide prototypes in CMOS 130 nm 1P8 M process at terahertz spectrum. Two types of mode converters(Complementary-Conducting-Strip Transmission Line and tapered transmission line) were simulated to feed the CMOS SIW. At the same time, the dissertation derives the S-parameter de-embedding method to obtain the SIW guided-wave complex propagation constants free from the discontinuity feeding network. Using a terahertz on-wafer measurement system to measure the CMOS SIW prototypes, the dissertation compares the measured data with theoretic values with excellent agreement to the best precision achieved in the laboratory. To validate the matching circuits, the dissertation describes the on-wafer measurement system environment coupled to the device under test, and verifies the leakage characeristics by mode charts and the three-dimensional fields plots.In addition, analyzing the stop band modal behaviors discussed in other articles, the dissertation includes the space harmonics to make proper mathematical and physical expressions mode completeness point of view, and explores the mechanism establishing the complex mode regions that will describe the stopband behaviors of the guided-wave structure correctly. The anomalous complex modes region corresponds to the results of the coupling of a pair of a forward wave and a backward wave space harmonics. The dissertation also presents the space harmonic dispersion curves, and changes the gap dimension between vias to observe the mode coupling of the adjacent space harmonics. The three-dimensional electromagnetic field analyses were carried out to investigate the stopband behavior dictated by the complex modes inside and outside the waveguide wall, as well as the operating frequency above the complex region.Lastly, the dissertation proposes two periodic monolithic synthetic structures: THz leaky-mode synthetic transmission line and composite right/left-handed transmission line, and reports the extensions the GSM/FEM method to solve the proposed two structures and obtain the modal dispersion curves validated by comparisons to the early publications. In summary, the dissertation resolves the anomalous propagations of the SIW lasting for nearly two decades, and proposes a generic approximation method that enables accurate assessment of complex propagation constants of planar transmission lne structures.