Designs for High Rejection Cavity Bandpass Filter Using Coaxial Resonator Structure

• Main Authors: Hou-Yueh Huang, 黃侯越
• Other Authors: Shih-Syou Li
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/utxy4n

碩士 === 國立臺北科技大學 === 電子工程系研究所 === 103 === Two designs for cavity-based bandpass filters using coaxial resonators are presented in this thesis. They are combline and interdigital filters, respectively. The resonant capacitance is increased through the structural changes of the resonators, which leads to the size reduction of the bandpass filters. The method of coupling coefficients is employed to search for corresponding external quality factors and internal coupling coefficients. Then the dimensions of the resonators are determined via electromagnetic simulation tools. Both designs choose Chebyshev frequency response. A coaxial stepped-impedance lowpass filter is also presented to suppress the harmonic responses of the bandpass filters. The design chooses dielectric material to replace air, which leads to dual-dielectric coaxial structures for the inductive sections of the lowpass filter. The advantages of the dual-dielectric structures reside not only on the ease of assembly, but also size reduction of the unit. The impedances and the effective dielectric constants of the dual-dielectric transmission lines are determined through the electromagnetic field distributions within the structures. The combination of the proposed bandpass filters and the lowpass filter results in high-rejection bandpass filters. The simulation results are verified experimentally. Good agreements are observed.