1.8GHz微小型高溫超導微波帶通濾波器之研究

Abstract

本論文主要之目的為利用準橢圓濾波器的合成方式，設計出在有限頻率的範圍內，產生一對傳輸零點的窄頻高選擇性的帶通濾波器。並利用交錯耦合特性的優點，藉由微小化共振腔彼此之間距的調整，來產生適當的耦合值，如此一來，便可實現出該對零點。此外，0o饋入結構的使用，還能產生額外的一對傳輸零點，因此通帶邊緣陡峭度可再提升。現在，已製作出用脈衝雷射濺鍍方式，將釔鋇銅氧超導薄膜鍍在1×1 cm2的鑭鋁氧單晶基板雙面的1.8G微小化交錯耦合型的平面式微波濾波器。由量測的結果顯示，其具有低插入損耗及窄頻帶邊緣陡峭的優勢，有潛力應用在無線通訊工業。

In this thesis, the quasi-elliptic filter synthesis method is used to design highly selective narrow bandpass filters which produces a pair of transmission zeros at finite frequency. Then we take advantage of the cross coupling property by adjusting the relative spacing among the miniaturized resonators to establish adequate couplings to produce a pair of finite frequency zeros. Besides, a zero-degree feed structure, which can create a pair of extra transmission zeros, and hence the out-of-band rejection of the designed filter is improved. The 1.8GHz miniaturized cross-coupled planar microwave filters fabricated using YBCO superconducting thin films deposited on both sides of a 1×1 cm2 LaAlO3 single crystal substrate by pulsed laser deposition. From the measurement results, the advantage of low insertion loss and sharp band edge skirts are attractive candidates for wireless communication industry.