| Summary: | 碩士 === 義守大學 === 電子工程學系 === 91 === As the dramatically increasing of broadband application in wireless systems, the demands of broadband antenna thus increase as well. Among those broadband antennas, leaky-wave microstrip antennas have earned great attention because of their light weight, compactness and ease to fabricate. Besides these advantages, electromagnetic waves in this kind of antenna radiating while propagating can provide broader bandwidth. In addition, the employing of double-layer structure offers leaky-wave microstrip antenna more various parameters to adjust in order to satisfy various demands. Among these parameters, when the width of the strip on the substrate varies from uniform to tapered geometry, the cut-off frequency of leaky-wave microstrip antenna also increases as strip width reduces. For this reason, electromagnetic wave that original cannot radiate under uniform structure can also propagate and contribute radiation. The phenomenon of bandwidth enhancement was confirmed by experiments, but theoretical analysis is not sufficient yet. However, to perform the analysis requires phase and attenuation constants, which could be a tough job due to the complexity of the tapered structure. Hence, this dissertation suggests that the stepped function is used to approximate the original tapered structure and solve for complex propagation constant of each antenna section. The approach is verified by bandwidth and reduces computational efforts. Moreover, the electric filed and current distribution of this antenna can be also obtained for future analysis. The antenna parameters of the tapered double-layer leaky-wave microstrip antennas can be used to compute other antenna parameters such as far-field radiation and input impedance, therefore antenna characteristics can be controlled effectively for future applications.
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