| Summary: | 碩士 === 國立臺灣科技大學 === 電機工程系 === 100 === 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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