A Study on Miniaturized Dual-mode Bandpass Filters with Tunability

• Main Authors: Hung-Wei Hsu, 許紘瑋
• Other Authors: Tzyh-Ghuang Ma
• Format: Others
• Language: en_US
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/85058070077754090187

碩士 === 國立臺灣科技大學 === 電機工程系 === 97 === Novel miniaturized ring dual-mode bandpass filters are developed by utilizing artificial transmission lines in either symmetrical or asymmetrical form. The miniaturized designs are developed by replacing the transmission lines in the ring resonators by artificial ones. The essentials of the ring resonators, which include the design principles and structures, are first discussed. The artificial transmission lines are then investigated in detail in terms of the design concepts, lumped equivalent circuit model, simulated and measured results, and the nonlinear phase responses. A miniaturized ring dual-mode single-band bandpass filter with harmonic suppression characteristics is designed with the asymmetrical artificial transmission lines. The circuit size of the filter is merely 0.167 λg × 0.087 λg, which corresponds to a size reduction percentage of 85.5% as compared with a conventional design. By introducing multiple transmission zeros with the asymmetrical artificial transmission lines and the modified input/output saw-toothed coupling structures, the proposed filter demonstrates wideband harmonic suppression characteristics. A miniaturized ring dual-mode dual-band bandpass filter using symmetrical artificial transmission lines is also proposed and discussed. The circuit size of the filter is 0.186 λg × 0.123 λg, which is only 22.5% the size of a conventional ring dual-mode filter. By simply adjusting the interdigital capacitance values of the artificial transmission lines, the cut-off frequencies and nonlinear phase response of the artificial lines can be readily controlled, which in turn determine the center frequrncies of the first and second passbands of the filter and the associate frequency ratio between them. The tunability and flexibility of the proposed miniaturized ring dual-mode dual-band filter are therefore improved.