Miniaturized and Large-division-ratio Rat-race Coupler Using Novel Transmission Line Elements and Dual-band Couplers with Arbitrary Power Division Ratios and Phase Differences
|關鍵字:||耦合器;雙頻;任意設計功率分配比;任意設計相位差;Coupler;Dual-band;Abitrary Power Division ratio;Abitrary Phase Difference|
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。
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.