| Summary: | 碩士 === 國立交通大學 === 電信研究所 === 85 === A simple structure formed by two metal patches
symmetrically deposit- ed at the two sides of the center
microstrip is proposed and analyzed for shielding the higher-
order modes in a waveguide-packaged micro- strip line
circuit. Two packaging waveguide sizes were considered and
compared. The variations (with the patch width) of the effective
die- lectric constants and field distributions, of the modes
in the pack- aged microstrip line with infinitely long side
patches, were first investigated using the 2-D finite element
method and the method of lines. The results suggested that
there exists a range of patch width at which the field
distributions of the higher-order modes are total- ly
different from those of the microstrip line without side
patches. The scattering of the patches, as a function of the
patch length and width, was then studied using the 3-D finite
element method with edge elements. It has been found that, by
simply choosing appropriate patch sizes, the parasitic
higher-order modes can completely shielded without
sacrificing the normal propagation of the dominant mode.
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