具寬截止帶與傳輸零點之耦合線帶通濾波器

本論文提出一系列具有延伸截止帶與較佳選擇度之耦合線帶通濾波器,其中包含了數個微帶線架構與兩個共面波導濾波器。這些濾波器可分別運用於不同需求之無線通訊系統中。首先,根據濾波器之基本理論及耦合節線之等效電路,在第二章提出基本型之耦合線帶通濾波器。藉由在傳統耦合線帶通濾波器中加入集總元件反轉器, 基本型耦合線帶通濾波器之階數可增加為傳統耦合線帶通濾波器的兩倍,並且不會增加電路面積與產生双倍頻效應。在延伸截止帶方面,根據基本型之耦合線帶通濾波器,在第三章運用縮短型耦合節線之內在傳輸零點來抑制奇數倍之倍頻響應,並藉此發展出具有延伸截止帶之新型微帶線耦合帶通濾波器。此方法具有不會增加電路面積與植入損耗之優點。在改善選擇度方面,第四章提出數個微小型微帶線耦合帶通濾波器,並且運用電容性或電感性之交叉耦合來產生多數個傳輸零點。並且傳輸零點之頻率可藉由變化交插耦合之電容或電感值來調整,以便改善濾波器之選擇度。最後,為了克服微帶線架構之缺點,第五章提出兩個具有良好選擇度與截止帶響應之微小型耦合線共面波導帶通濾波器。與傳統型耦合線帶通濾波器運用了二分之一波長共振器來比較,由於此共面波導帶通濾波器運用了四分之一波長之共振器來實現,所以尺寸只有傳統型濾波器之ㄧ半,而且不會在兩倍中心頻率處產生倍頻效應。另外,此共面波導帶通濾波器也採用了第三章與第四章之概念來達到延伸截止帶與較佳選擇度之目標。

關鍵字

濾波器；耦合線；傳輸零點；截止帶

並列摘要

In this dissertation, a new class of coupled-line bandpass filters (BPFs) with stopband extension and better selectivity, including several microstrip and two coplanar-waveguide (CPW) structures, is presented. These BPFs can find applications in various wireless communication systems. First of all, in Chapter 2, the basic coupled-line BPFs are proposed according to the fundamental concepts of filters and equivalent-circuit models of coupled-line sections. By adding the lumped-element-inverters into conventional coupled-line BPFs, the order of proposed coupled-line BPFs are double of conventional coupled-line BPFs without increasing the circuit area, and no repeated passband is observed at twice center frequency. For the stopband extension, in Chapter 3, the basic coupled-line BPFs are extended to implement the novel microstrip coupled-line BPFs with extended rejection band, using the transmission zeros inherently associated with the shortened coupled sections to suppress the odd spurious harmonics. This technique has the advantage of compact circuit size without increasing the insertion loss. For the selectivity improvement, several compact microstrip coupled-line BPFs with capacitive or inductive cross-couplings to create multiple transmission zeros are proposed in Chapter 4. The locations of transmission zeros can be adjusted by varying the values of cross-coupled capacitances or inductances so as to improve the filter selectivity. Finally, in order to overcome the drawbacks of microstrip structures, two compact coupled-line coplanar-waveguide bandpass filters with good selectivity and stopband responses are proposed in Chapter 5. By using the quarter-wavelength resonators in implementation, the filter size can be reduced by half and no spurious passband is observed at twice the center frequency when compared with the conventional parallel-coupled bandpass filters based on half-wavelength resonators. In addition, the concepts in Chapters 3 and 4 are also adopted in the CPW filters design so as to achieve stopband extension and better selectivity.

並列關鍵字

filter ； coupled-line ； transmission zeros ； stopband extension

參考文獻

[1] B. Easter and K. A. Merza, “Parallel-coupled-line filters for inverted-microstrip and suspended-substrate MICs,” in Proc. 11th European Microwave Conf., Oct. 1981, pp. 164–167.

[2] C.-Y. Chang and T. Itoh, “A modified parallel-coupled filter structure that improves the upper stopband rejection and response symmetry,” IEEE Trans. Microwave Theory Tech., vol. 39, no. 2, pp.310-314, Feb. 1991.

[3] K. F. Chang and K. W. Tam, “Miniaturized cross-coupled filter with second and third spurious responses suppression,” IEEE Microwave Wireless Compon. Lett., vol. 15, no. 2, pp. 122–124, Feb. 2005.

[4] M. Sagawa, M. Makimoto, and S. Yamashita, “Geometrical structures and fundamental characteristics of microwave stepped-impedance resonators,” IEEE Trans. Microwave Theory Tech., vol. 45, no. 7, pp. 1078-1085, July 1997.

[5] S.-Y. Lee and C.-M. Tsai, “New cross-coupled filter design using improved hairpin resonators,” IEEE Trans. Microwave Theory Tech., vol. 48, no. 10, pp. 2482-2490, Dec. 2000.

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具寬截止帶與傳輸零點之耦合線帶通濾波器

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