| Summary: | 碩士 === 國立臺灣大學 === 電信工程學研究所 === 90 === Filters play important roles on RF/microwave applications. Many emerging applications such as wireless communication systems call for stringent requirements-- smaller size, lower cost, narrower bandwidth and higher quality factors. Two structures of filters suitable for narrowband applications are investigated in this thesis and their characteristics of frequency responses are compared.
For the first structure, coplanar waveguide is selected as the transmission line and shunt stubs are selected as impedance inverters to design the inductive-coupled bandpass filters on Ka-Band. Due to the removal of the gaps, it can exhibit lower radiation loss as compared with the commonly employed capacitive-coupled filters. The second structure is based on the dual-mode ring filter which has an excellent characteristic of the controllability for the attenuation frequency. Moreover, two kinds of implementation have been investigated and their frequency responses are compared. Finally, a simple way is proposed to achieve very sharp outband-rejection by cascading two kinds of ring filters with an impedance-matching transmission line. It has the performance of four-stage filter but occupies smaller size than others.
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