微型化環形諧振腔帶通濾波器

Abstract

本論文研究數種具有雙模環形諧振腔之帶通濾波器。論文先回顧環形諧振腔的架構與原理，接著探討非對稱之環形諧振腔與微擾源和饋入位置的關係。藉由傳輸線理論，可得到傳輸零點和共振模態的設計方程式，並繪出對應的設計曲線。運用以上所得到的設計曲線，非對稱電感性微擾之環形諧振腔可設計準橢圓響應之雙模帶通濾波器。本文另外提出螺旋式電感的架構，將全波長的環形諧振腔繞成雙環，以達成電路的微型化。在該微型化電路中，電感性的微擾源和雙環之間的連結，是藉由共平面波導的短高阻抗線段以及兩個貫孔實現。 本論文的第二部分以接地環形諧振腔設計具有兩個傳輸極點之二階帶通濾波器。電路中兩個共振模態分別由電容性和電感性耦合控制。並且藉由選擇對稱和非對稱饋入架構以及模態間的耦合特性加以控制傳輸零點之個數和位置。根據傳輸線理論的分析，利用對稱的饋入架構和以電容性為主的模態間耦合，兩個傳輸零點可被設計在二階帶通濾波器的通帶兩側。除此之外，在對稱饋入的架構下，藉由降低輸入與輸出端之電感性耦合，亦可提高其截止帶中的衰減量。接地環形諧振腔的電路微型化以及截止帶的拓寬可藉由開路殘段和短路耦合線所組成之架構達成。最後，再運用指叉式電容，本文亦實現一個超微型之二階帶通濾波器，面積僅為傳統環形諧振腔的8.8%。由結果顯示，所有電路的模擬結果與量測數據相當一致。 論文的最後一個部份提出結論，並闡述未來的研究。

This thesis investigates ring resonator with two resonant modes and its implementation of miniaturized bandpass filters. In the beginning, we briefly review the conventional ring resonator filter, and then show the frequency responses of asymmetric dual-mode ring resonator filters with various perturbation types and feed positions. By using the transmission-line theory, the equations for resonance modes and transmission zeros are derived to plot useful design curves. The quasi-elliptic function response filter can be implemented by an asymmetric dual-mode ring resonator with the inductive perturbation. To obtain a miniaturized circuit area, the 1- ring trace is folded into a spiral or a double-ring configuration. The inductive perturbation in the spiral-ring resonator is chosen as the crossover and implemented by two via-holes and a short high-impedance CPW interconnection in the ground plane of the microstrip. Secondly, shorted ring resonator evolved from a 1- ring resonator is proposed to design a second-order bandpass filter. The two resonant modes are separately controlled by the inductive and capacitive coupling, respectively. With proper symmetric/skew-symmetric input/output tapped structure and type of inter-stage coupling, transmission zeros can be created and analytically determined. Based on the transmission-line theory, the second-order bandpass filter with two transmission zeros on the both sides of passband can be devised by symmetric feed and electric-dominant inter-stage coupling. Moreover, the rejection in stopband can also be effectively improved by reducing the inductive coupling between the I/O ports. To achieve the size reduction and stopband extension, the open stub and shorted coupled-line section are employed to implement a new proposed resonator. Furthermore, with the aid of interdigital fingers, an ultra-compact shorted ring resonator bandpass filter can be obtained. All the measured results of fabricated circuits have good agreement with the simulated results. Finally, a concluding remark is given, and suggested future work are discussed