摘要
本論文提出小型化耦合線帶通濾波器，其具有面積小、高選擇度及良好的通帶外衰減性等特性。此架構以四分之一波長共振器設計，因此在兩倍中心頻率附近不會有寄生通帶（spurious passband）產生，而且可藉由在傳統耦合線段額外接上電容或電感的方式，來縮短耦合線的長度。此外，由於引入了電容性或電感性的交互耦合（cross-coupling）機制，在通帶附近產生傳輸零點（transmission zero），同時提高選擇度。用來實現阻抗反轉器（K-inverter）的開路截線，也可以在高頻產生傳輸零點來抑制倍頻的寄生通帶。在建立了等效電路模型及設計公式之後，完成小型化耦合線帶通濾波器的設計與研究。最後成功製作了四階與六階的小型化帶通濾波器，皆具有高選擇度的特性，且一直到四倍中心頻率附近都沒有寄生通帶產生，與傳統的平行耦合線濾波器相比，尺寸可縮小百分之六十以上。
並列摘要
Compact parallel-coupled bandpass filters with good selectivity and better stopband rejection are proposed in this study. They are designed with quarter-wavelength resonators such that there is no repeated passband at twice the center frequency, and the lengths of coupled-line sections can be reduced by using additional capacitors or inductors. In addition, by introducing the capacitive or inductive cross-coupling effect, transmission zeros can be achieved to improve the selectivity. The open stub which works as a K-inverter can also introduce a transmission zero at high frequency so as to suppress the spurious passband. Suitable equivalent models and design formulas are establish, from which the proposed filter can be design and investigate. Finally, compact 4th and 6th order bandpass filters with better selectivity and wider stopband up to four times the center frequency are accomplished. Comparing to the conventional parallel-coupled bandpass filter, the size reduction is over 60%.