| Summary: | 碩士 === 國立臺北科技大學 === 電腦與通訊研究所 === 101 === A study is aiming to improve the bandwidth of trans-directional coupled-line coupler by cascading multi-section coupler. Directional coupler are microwave passive devices featuring the functions of dividing and combing power and maintaining phase relationship between output ports. Microstrip coupled-line couplers are one way to implement directional couplers. For microstrip coupled-line couplers loaded with periodic elements, the designs not only increase the coupling coefficients and reduce the electrical lengths of the coupled lines, but also realize trans-directional coupler. However, compared to traditional microstrip coupled-line couplers, the periodically-loaded microstrip coupled-line couplers can only offer narrower bandwidth, which results in their limitation for wideband applications. The traditional multi-section couplers in series connection offer a solution for this problem by simply replacing each single traditional coupler by a periodical-loaded coupler. In this thesis, not only analysis cascading method of trans-directional coupler, but also design maximum-flat and equal-ripple three-section trans-directional coupler. The commercial EM simulation tools, HFSS and ADS, will be employed to simulate the proposed designs. The simulation results will be verified experimentally to confirm the feasibility of the broadband three-section periodically-loaded trans-directional couplers.
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