本論文研究目標為研製小型且具有高隔絕度的多工器。一般的均勻阻抗共振器除了中頻以外也會在其倍頻時共振，而為了研製高隔絕度的多工器，必須要將其倍頻壓抑已減少輸出埠之間的干擾。本論文主要以一長饋入線當作電路的主要架構，並觀察其電流密度分佈，了解在不同擺放位置的耦合型態。而為了將此物理概念量化，本論文萃取了耦合係數和外部品質因素，並藉由將共振器擺放在與其倍頻耦合型態相反的位置以達到倍頻壓抑的效果。接著用此濾波器架構當作基本單一的電路，並提升濾波器設計數目來設計多工器。而此架構所設計的三工器和四工器其量測的隔絕度皆大於40dB。此外，相較於其它有關的論文著作，此論文所提出的架構也有較少電路面積的特性。為了再進一步減少電路設計的面積，本論文將進一步使用步階阻抗共振器來取代均勻阻抗共振器。相較於使用均勻阻抗共振器，使用此架構將會有更小的電路面積跟更高的隔絕度。而上述所研製多工器的設計頻帶皆較為分散，此論文最後將設計一鄰近通帶的三工器，而其同時也具備高隔絕度的特性。Compact microstrip multiplexers with high isolation are proposed in this thesis. The uniform impedance resonator would resonate at its center and harmonic frequency. To achieve high isolation between channels, the filter is design to suppress its harmonics. To qualify the coupling between the feeding line and resonator, the external quality factor and coupling coefficient are extracted. And this basic block filter is used to design multiplexer. The measured isolations amongst channels are over 40 dB. In comparison with the previous work, the proposed multiplexers perform the feature of high-isolation and compact size. Besides, stepped impedance resonator is used to reduce circuit size. In comparison with the one using uniform resonator, the design using stepped impedance resonator shows smaller circuit size and high isolation. The passbands of the above-mentioned multiplexer are designed at arbitrary frequencies. In this thesis, the triplexer whose passbands design at near frequencies is presented. And this proposed triplexer still has a feature of high isolation.
