| Summary: | 博士 === 元智大學 === 電機工程學系 === 94 === The theme of studying in this thesis is high frequency techniques for the characteristic analysis of reflector antennas. Reflector antennas have unique features of high directivities and low sidelobe levels, and thus are widely employed in many applications of the point-to-point and satellite communications. At first, I will drive an effective approximate electromagnetic mathematic models for the efficient estimation of the rotationally symmetric Parabolic Reflector Antenna’s Performance. In this thesis, effective formulations based on approximate electromagnetic (EM) mathematic models are developed to efficiently estimate the spillover and aperture efficiencies of rotationally symmetric parabolic reflector antennas. The EM mathematic models employ cosine and sine functions with fractional powers to approximate the co-polarized and cross-polarized components of the fields radiated from the antennas feeding to the reflectors, where the closed form solutions of spillover and aperture efficiencies are then obtained. In distinguishing from previous works where only cosine tapers with integer powers are employed to model the co-polarized components of the feed’s radiation and the cross-polarized components are ignored, the present work is a broad extension of it.
A highly efficient Guassian beam (GB) method was recently developed to provide a relatively rapid analysis of large perfectly conducting reflector antennas. This GB method is very efficient because it represents the feed radiation in terms of a set of very few rotationally symmetric GBs and provides an essentially closed form solution for the reflection and diffraction of each GB incidence on the reflector surface. The time consuming numerical integrations in the evaluation of radiated fields over the large reflector surfaces that are generally required in conventional approaches of the physical optics and aperture integration techniques are completely avoided. This paper extends the previous works to treat reflector antennas with dielectric surfaces that derive from many practical applications including for instance the analysis of the scattering from sub-reflectors having frequency selective surfaces in a dual-reflector antenna system.
The developing trend of reflector antennas involves with the utilization of impedance reflecting surfaces. In many applications, such as in the compact range
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