本論文中提出一應用於無線通訊系統(WiMAX)的雙工器與三工器，主要在改善傳統雙工器及三工器的連接方式。本次設計的雙工器結合了兩個帶通濾波器，分別為四分之一波長及二分之一波長共振器的帶通濾波器，因此旁生通帶可以被壓抑，不會影響高頻的濾波器，使隔離度可以提升。而在連結兩個濾波器時以共用耦合線饋入的方式，取代傳統雙工器用T接面(T-junction)連接濾波器，使得雙工器在輸入端匹配時，電路面積可以更進一步縮小，完成一個隔離度優於30 dB的雙工器。在三工器的部分，考慮一條微帶線在單一平面上最多只能與兩條微帶線耦合，所以我們將其中一個二分之一波長帶通濾波器用槽孔耦合的方式實現，利用將接地面開一個槽孔的方式，使訊號可以經由槽孔耦合到下層的饋入線，讓上層的傳輸線，除了耦合到相鄰的耦合線外，也可以經槽孔向下耦合到下層電路，完成連結的匹配，實現一隔離度優於20 dB的雙層板三工器。電路製作皆以FR-4 的板材完成，介電常數為1.6、介質損耗為0.02。從模擬與實作結果比較，皆具有很好的一致性。In the thesis, diplexers and triplexers for WiMAX applications are proposed. The proposed diplexer is mainly composed of a 1/2 ? and a 1/4 ? parallel-coupled-resonator bandpass filters. By using 1/4 ? parallel-coupled-resonator filter, the spurious passband will appear at 3f0. Thus, the isolation between two channels can be enhanced. In many conventional diplexer designs, T-junction is often used to connect both filters. This strategy could lead to the increase of the circuit area. Therefore, instead of the T-junction, common coupled lines are used to connect these two filters. By using the proposed matching network, a compact diplexer of high isolation (>30 dB) is thus obtained. In the triplexer dsign, the third filter is added to the diplexer mentioned above. The signal is coupled to the third filter from the top layer to the bottom layer through the slot aperture on the ground. Then, we implemented input matching network of the triplexer without increasing extra area. The measured isolations of triplexer among channels are all better than 20 dB. All circuits are fabricated y using FR-4 substrate. The relative permittivity and loss tangent of the substrate are 4.4 and 0.02, respectively. The measured results are in agreement with the simulated results.
