本論文提出一款具串聯LC諧振器之新型合成傳輸線。該合成傳輸線以曲折線電感與串聯LC諧振器組成，不但可利用慢波結構縮小電路尺寸外，亦因串聯LC諧振器於共振時虛接地特性，產生高頻傳輸零點；同時，經合成傳輸線之適當佈局規劃，該高頻零點更可使合成傳輸線於特定頻率具有開路輸入阻抗，具以實現雙模態操作之能力。本論文詳盡討論此創新合成傳輸線之設計理念、電路架構、等效集總電路模型、模擬與量測結果、及實際應用等。
本論文提出該新型合成傳輸線之創新應用，包含：具寬廣上止帶之微型化枝幹耦合器、微型化雙工器與雙模態耦合元件。數款微小化電路皆成功驗證該合成傳輸線之效能，使電路在保有原操作頻帶電器效能之前提下，有效降低電路面積，並可實現雙模態操作或止帶抑制之能力。
利用雙模態耦合元件，搭配雙頻帶耦合器，本論文創新實現一款雙模態相位陣列天線系統，該系統為獨創設計，未見於文獻記載。此系統於低頻帶具有波束切換天線陣列之響應，而於高頻帶則有信號回溯陣列之特性；其輻射場型之量測結果，可充分驗證該雙模態相位陣列系統之設計架構。此創新構想將可擴展相位陣列天線之應用情境。

A novel synthesized microstrip line with series LC tanks is proposed in this thesis. The proposed synthesized line is formed by series LC tanks and meander line inductors. It features not only slow-wave properties for miniaturization, but an out-of-band transmission zero due to the virtual short-circuit of the LC tank in resonance. By properly adjusting the layouts of the quasi-lumped elements, the input impedance of the synthesized microstrip line can be nearly open-circuited, therefore enabling the ability of dual-mode operation. The design concept, circuit configuration, equivalent lumped model, simulated and measured results and practical applications of the synthesized microstrip lines are carefully investigated and discussed.
Base on the synthesized microstrip lines, three novel circuit designs, namely the miniaturized branch-line coupler with wide upper stopband, the miniaturized diplexer, and the dual-mode couplers, are developed and discoursed in this thesis. These size-reduced designs, in addition to demonstrating comparable in-band responses as their conventional counterparts, provide the ability of out-of-band rejection or dual-mode operation simultaneously. They clearly sustain the performance of the synthesized microstrip lines.
In chapter 4 of this thesis, a novel dual-mode phased array antenna is also proposed and implemented using the dual-mode/dual-band directional couplers. The proposed architecture is original, and has never been reported in the open literature. This dual-mode array behaves like a switched-beam array and a retro-directive array, respectively, in the lower and upper operating bands. The measured radiation patterns clearly validate the design concept of the proposed array. This dual-mode system could extend the application range of the phased array antennas.

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