本論文介紹了四種雙頻帶帶通濾波器，在步階式阻抗共振器的基礎上，具有可控制的頻率比。為了改善步階式阻抗帶通濾波器的選擇度及頻率比，在共振器兩端開路端彼此耦合。而耦合線間耦合結構可化為等效電路，可使用奇偶模分析計算出與物理結構上不同的電氣長度。除此之外，在兩通帶間產生新增的兩個零點，比起典型的步階式阻抗濾波器有較好的止帶表現。 第一個電路是典型的二階步階式阻抗帶通濾波器，兩通帶的中心頻率為1GHz 及3.6GHz。第二個電路是具有自耦合結構的二階步階式阻抗帶通濾波器，兩通帶的中心頻率為 1GHz 及 4GHz，可以很明顯的理解到自耦合線的結構能增加其兩通帶間的頻率比。第三個電路是在第二個電路上增加源載間的弱耦合結構，可以看出耦合部分對於兩通帶中心零點位置的影響。為了增強自耦合線的影響，這裡介紹了第四個電路結構，將原本的自耦合部分取代指叉式電容以滿足更高的耦合係數需求，兩通帶的中心頻率為 1.1GHz 及 4.8GHz，以上的四種電路結構皆採用相同的阻抗比。;In this thesis, four structures of dual-band bandpass filter(BPF) are introduced. Base on the step impedance resonator(SIR), the dual-band BPF has a controllable frequency ratio. To improve selectivity and the range of frequency ratio, two open-ended arms are coupled by each other. Because of the equivalent circuit in coupled-lines, different electric lengths can be calculated by even and odd mode analysis. In addition, two addition transmission zeros(TZ) that appear between two bands make rejection in stopband better than the typical SIR filter. The first circuit is a typical two-order SIR bandpass filter. The center frequency of the two pass-band are 1GHz and 3.6GHz.The second circuit is a two-order SIR bandpass filter within the self-coupled structure. The center frequency of the two pass-band are 1GHz and 4GHz. There is obviously realized self-coupled lines can increase the frequency ratio between two pass-band. The third circuit is the second circuit adding weak coupling between source and load. There can be found that the coupled-line section is closely related to the position of central TZ. In order to enhance the effect of self-coupled lines, the fourth circuit is introduced in this thesis. Replace the self-coupled section with interdigital capacitors to satisfy higher coupling coefficient. The center frequency of the two pass-band are 1.1GHz and 4.8GHz. These four structures are all using the same impedance ratio.
