本篇論文所提出步階式阻抗負載殘段共振器的架構來設計具有寬截止頻帶的帶通濾波器。首先在步階式阻抗負載殘段共振器的頻率響應分析中，將利用步階式阻抗共振器的特性如藉由調整阻抗比與電子長度比，來控制其共振器的倍頻頻率與傳輸零點頻率，再將此結果應用在設計濾波器上，可以在不使用額外的電路之下，利用本身電路的結構達到倍頻壓抑的效果，使電路面積能縮小化。將使用此共振器架構研製出兩種不同中心頻率的二階雙頻帶通濾波器，其中一種為兩通帶的中心頻率為鄰近頻帶(near band)的雙頻帶通濾波器。再利用上述的共振器研製出高階數的雙頻帶通濾波器，其中包括一個三階與兩個四階的雙頻帶通濾波器，這當中共振器之間的交錯式耦合或是反對稱式饋入來使通帶附近產生傳輸零點，使其增加通帶的選擇性。以上所述的雙頻帶通濾波器皆具有寬截止頻帶。最後繼續沿用此共振器結構，使用指叉式耦合饋入的方式研製出具有寬截止頻帶的寬頻帶通濾波器。 In the thesis, the proposed structure, stepped-impedance stub-loaded resonator(SISLR), is utilized in the bandpass filter featuring wide stopband. To begin with, use characteristics of SISLR to control spurious passband and transmission zeros by adjusting impedance ratio and electrical length ratio. Afterward, the results are applied to design filters. The spurious passband is suppressed by the circuit itself instead of adding extra circuit. Consequently, the size of the circuit is minimized. We will take advantage of the proposed structure to fabricate two 2nd-order dual-band bandpass filters with different fundamental frequencies. One is that two fundamental frequencies of the passband are near band, and the other is based on the above filter to develop high-order filters, including one 3rd-order and two 4th order dual-band bandpass filters. Transmission zeros near two sides of the passband result from cross coupling or asymmetric feed line; therefore, the selectivity is enhanced. As mentioned above, all of these dual-band bandpass filters possess wide stopband. Eventually, the proposed resonators can be integrated with the interdigital coupled feed line to attain wide stopband.
