本論文主要係使用新式電路結構實現微波分枝耦合器、雙頻帶環形耦合器及被動隔離元件。分枝耦合器部分，本論文使用集總非對稱E型結構設計分枝耦合器，以提供較佳之操作頻寬。但非對稱E型結構使用過多集總元件，論文中進一步使用元件數較少的非對稱π及T型結構取代，有效地減少總集總元件個數，降低製作成本。雙頻帶環形耦合器部分，本論文主要係使用L型結構設計雙頻帶環形耦合器，L型結構係由一段傳輸線及串聯集總共振器所組成，可提供雙頻操作特性。基於該電路架構，本論文研製五種不同型態的環形耦合器，其中微型化雙頻帶環形耦合器之電路面積縮小為傳統電路之10 %。被動隔離元件部分，本論文使用開槽耦合微帶線耦合器研製寬頻被動隔離元件，該元件之Tx及Rx埠間30 dB量測隔離度頻寬為44.9 %。相較於商用元件，本論文所設計之被動隔離元件可提供較寬頻的反射損失、較佳的穿透損失及較寬頻的隔離度。

The aim of this thesis is to develop microwave branch-line couplers, dual-band rat-race couplers, and the passive isolation component based on new circuits structures. For the branch-line coupler design, asymmetrical E-equivalent sections are used to design lumped-element branch-line couplers with the improvement of the return loss bandwidth. To reduce the number of lumped-elements, in this thesis, the asymmetrical E-equivalent section is further evolved into asymmetrical π- and T- equivalent structures for the branch-line coupler design. For the dual-band rat-race coupler design, L sections are exploited to design dual-band rat race couplers. The L section is composed of a transmission line and a series LC resonator to have the dual-band property. By using L sections, this thesis develops five types of dual-band rat-race couplers. The miniaturized dual-band coupler only occupies a 10 % circuit size of the conventional one at the center frequency of the 1st passband. For the passive isolation component design, three sets of diamond-shape slot-coupled microstrip lines are integrated into a passive isolation component. Since the slot-coupled microstrip can provide a wideband and accurate quadrature phase difference, the developed passive isolation component can effectively improve the isolation level and bandwidth between transmitting and receiving ports. The developed isolation component has a 30 dB isolation of 44.9 %.

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