| Summary: | 碩士 === 義守大學 === 電子工程學系碩士班 === 95 === The CP (circularly polarization) antenna has been popular in the long distance communication due to its high noise-tolerant capability. Among many CP antennas, the semi-ring leaky-wave antenna with double-layers overcomes the shortcoming of traditional spiral antennas, and it can radiate broad-band CP electromagnetic wave only with a simple single-feeding. The advantages of the double-layer structure can easily match input impedance of antenna, and the CP band is adjustable based on demands. But the analysis on this antenna is not completed due to its complicated structure, and application is thus limited. Therefore, the purpose of this thesis is to establish the analysis theory for this CP antenna, as well as understand its concept and characteristics. First, this thesis introduces the CP concept by theoretical data. Later, the analysis of a single-layer semi-ring antenna is applied to double-layers ones. After appropriate process, the use of cavity model effectively obtains antenna characteristics, including propagation behavior, electrical distribution, radiation pattern and CP performance. The agreement between theory and simulation proves the validity of proposed method here. Besides, this thesis does not only summarizes the flow chart to design this kind of CP antenna, but analysis results also confirm that this antenna can operate in broad CP bands. Moreover, the high degree of freedom from structure enables the antenna to have different frequency bands for operation. By the modification of simulation, those results obtained by cavity model are close to reality, the accuracy of results eases the use of this antenna. This thesis establishes the fundamental theorem for double-layers semi-ring leaky-wave antennas, and the provided data and results are also useful for future applications.
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