新穎人造傳輸線實現之縮小化及高功率分配比鼠競環耦合器與任意輸出埠功率分配比及相位差之雙頻耦合器設計

Abstract

本論文演示了兩種不同效能的耦合器。這兩種耦合器都能夠任意設計輸出埠的功率分配比。其中一種的結構設計方式，相較於傳統的鼠競環耦合器，在結構上有著大幅度的縮小。另一種耦合器設計，除了任意分配輸出埠功率外，還可以任意設計輸出埠相位差，並且能夠操作在任意雙頻。這兩種耦合器設計，都改善了傳統耦合器的效能。 前兩章就枝幹耦合器與鼠競環耦合器的用途演進與基本原理介紹。第三章提供了一種新穎的人造傳輸線，這種傳輸線在操作頻帶具備了高阻抗的特性，將其運用在傳統的鼠競環耦合器中，可以達到輸出埠的高功率分配。新穎人造傳輸線的設計方式，從等效集總元件模型出發。經過一連串的分析，得到集總元件值與等效阻抗的極點和零點的關係。藉由該關係式，可以協助控制通帶的阻抗與相位關係，達到設計的規格。利用高阻抗新穎傳輸線，最後在第三章得到了一個縮小化高功率分配比之鼠競環耦合器。該耦合器操作在3.5 Ghz，具備了12-dB的輸出埠功率分配比。以及相較於傳統鼠競環耦合器僅占用21 %的面積。並且在量測與模擬的數據上，有著很好的對應。 第四章提供了雙頻可任意設計功率分配比與相位差之耦合器的設計方式。運用奇偶模分析法，得到設計規格與結構參數間的簡明關係式。在雙頻設計上，也提供了完整的設計方式。此外，針對雙頻設計、功率分配以及相位差等規格，也建立設計規格與結構參數和頻寬的關係圖表。這些圖表可用以協助確立耦 ii 合器初期規格設計的可行性。為了證明設計流程的可用性，運用整套設計流程，實作了四種任意功率分配比與相位差的雙頻耦合器，量測數據與模擬數據相當的符合。這個具備多項效能結構簡單的耦合器設計，預期可以應用在波束形成的系統中，達到減化饋入網路的效果。

In this thesis, two types of couplers are presented. Both of them have features of arbitrary power division ratios. One of them has the large size reduction, which is compared with conventional rat-race coupler. The other one has the dual-band operation, and ability of arbitrary phase difference. The designs of these two couplers which improve performances of conventional couplers. The first two chapters introduce the applications, operating principal and theory of branch-line coupler and rat-race coupler. In the third chapter, a novel transmission-line element that is able to exhibit a high-impedance passband is proposed and applied for coupler realization with a large power division ratio. The analysis of the transmission-line element was conducted by its equivalent circuit model and the closed-form equations for the pole and zero frequencies of the effective impedance were derived to help control the passband impedance and phase responses by the lumped parameters. The high-impedance feature of the presented artificial line was exploited to experimentally develop a 12 dB ring coupler, which occupies only 29% footprint of the conventional coupler at 3.5 GHz. Experimental results are in good agreement with the simulation data. In the fourth chapter, a directional coupler that allows for arbitrary power division ratios as well as arbitrary phase differences at dual frequencies of interest. Explicit design equations in terms of dual-band power-dividing ratios and phase iv differences will be given here and were derived based on the even- and odd-mode decomposition analysis. To illustrate the design procedure, examples will be provided and the relevant studies on the coupler’s electrical parameters for a wide range of dual-band specifications and frequency ratio were conducted, by which the graphical solutions can be readily used as the further design tool. In addition, the resulting operational bandwidths are included and discussed for completeness. To validate our idea, four coupler prototypes were carried out according to the given guidelines. Excellent agreement is obtained between the measured and full-wave calculated results. The functional versatility of the proposed simple structure is well suited to applications in dual-band integrated modules, such as the beam-forming networks, for both loss and size reduction.