切換式多平面掃瞄CRLH洩漏波天線與三頻雙工環路器之設計

Abstract

本論文前半部提出一新型多平面掃瞄複合左右手(composite right/left handed, CRLH)洩露波天線之設計，採用後設材料(metamaterial)所擁有的獨特性質，將蕈狀結構與MIM(metal-isolator-metal, MIM)電容作結合，建構出一維平衡型CRLH 洩漏波天線，其擁有輻射波束隨頻率由後向至前向作連續性掃瞄之特性。接著將兩組一維平衡型CRLH洩漏波天線作十字交叉擺設，並於交叉點之電路單元旁設置射頻切換電路，藉由著控制二極體導通狀態而切換不同的洩漏路徑，使天線具有數個掃瞄平面可供選擇，為將波束切換與掃瞄功能合為一體之新型天線。此外，本設計採用平面印刷電路板技術所實現，其電路結構輕薄簡單，易與其他平面印刷電路作整合。 本論文後半部提出一種新型微波電路之設計，此微波電路稱為三頻雙工環路器，它亦基於後設材料之電磁帶隙(electromagnetic band-gap, EBG)性質所建構出。首先，將傳統單層蕈狀結構結合懸置微帶線之理論，推廣至多層結構，使其擁有多頻EBG特性，達到電路縮小化效果。接著將三組所設計的雙頻EBG 電路作環形串聯，並經過妥善的阻抗匹配，進而完成三頻雙工環路器之設計，它結合了雙工器與環路器之功能，適合在GSM 1800MHz、WiFi 2.45GHz 和WiMAX 3.5GHz系統之間，作多頻段與多通道的資料整合。

In the first part of this thesis, a novel CRLH leaky-wave antenna with multi-plane scanning capability is designed and fabricated. By utilizing unique properties of the meta-materials, a 1-D balanced CRLH leaky-wave antenna is realized with unit cells consisting of mushroom structures and MIM capacitors. Consequently, the radiation beam of the antenna is capable of continuous scanning from backward to forward angles. Furthermore, we place two sets of 1-D balanced CRLH leaky-wave antenna in a cross-type structure, and install RF switching circuits aside to the intersectional unit cell. By controlling those PIN-diodes, we can switch different leaky paths to achieve multi-plane scanning capability. This novel circuit combines the properties of beam-switching and beam-scanning antennas. In addition, all proposed elements of this invention are implemented by planar printed circuit board technique, which is low-profile, simple and easy to be integrated with other planar printed circuits. A novel three-port microwave circuit called triplex bi-directional ring-hybird is proposed in the second part of this thesis. It is accomplished on the basis of the electromagnetic band-gap (EBG) characteristic of the meta-materials. Firstly, we extend the concept of the traditional single-layered mushroom structure with the suspending microstrip line to the multi-layered structure. In this way, the multi-layered structure can reveal multi-band EBG characteristic and achieve miniaturization. Moreover, we use three sets of proposed dual-band EBG circuit to be series-connected in a ring-type structure. By using proper impedance matching, the design of the triplex bi-directional ring-hybird is completed. It combines the capabilities of the diplexer, the duplexer and the circulator. The triplex bi-directional ring-hybird can integrate three kinds of communication systems with each other, which operate at frequencies including GSM 1800MHz, WiFi 2.45GHz, and WiMAX 3.5GHz, respectively. It is suitable for the information integration of multi-band and multi-system communication applications.