microstrip bandpass filter
关于stripline，microstrip，CPW的区别已经有了画面感
这里要讲述三种微带线带通滤波器
参考一、使用了新的耦合方案的阶梯阻抗谐振器的双频段微带带通滤波器
Zhang Y P . Dual-band microstrip bandpass filter using stepped-impedance resonators with new coupling schemes[J]. IEEE Transactions on Microwave Theory and Techniques, 2006, 54.
It is known that a line with characteristic impedance Z0 can be represented as a parallel connection of two lines with characteristicimpedance 2Z0. Therefore, under condition Z‘2 =2Z2 andequal length, this new coupling scheme is electrically equivalentto the normal coupling scheme from the input to the direct port.However, it introduces tighter coupling from the input to thecoupled port and, thus, lower the insertion loss. This is provenas follows using the theory of transmission line.
参考二 使用了弯曲接替阻抗谐振器的双频段带通滤波器
Chen F C , Chu Q X . A compact dual-band bandpass filter using meandering stepped impedance resonators[J]. Microwave & Optical Technology Letters, 2008, 50(10):2619-2621.
此篇文章在很大程度上继承了上一篇的结构与理论，
这篇论文，这里的结构，emmm，属于玄学并没有什么理论支撑
it is necessary to select the proper distance between the two low impedance sections in the center, if S1<3.5 mm, the proposed filter will produce undesired responses,
By adjusting S properly, we could get the required response of the dual-band BPF. Meanwhile, the position of the transmission zero between the two passbands is changed while tuning S .
结论：没有结论