| Summary: | 碩士 === 國立高雄應用科技大學 === 電子與資訊工程研究所碩士班 === 95 === Due to the dramatically increasing of dual-band and wideband application in wireless systems, the demands of wideband antennas thus increase drastically. So, in this thesis, the CPW-fed dual-broadband T-type planar monopole antenna has been proposed at first. The use the electromagnetic simulation software can analyze antenna’s characteristics to help for further antenna designs. According to the idea of the previews design, the following CPW-fed dual-broadband tab-shaped planar monopole antenna is proposed. By varying the angle of this tab-shaped radiator, the dual-broadband operation can be obtained.
Basically, the conventional microstrip-line-fed slot antenna has its resonant mode. By embedding an open square-ring, it is found that the dual-band operation can be achieved. From studied results, the operating frequency of the higher mode can be shifted and than the frequency ration of the two resonant modes has a range of 1.41~1.97. Furthermore, as the embedded square-ring is opened more large, the dual-band operation can be also obtained. The frequency ratio has a range of 1.44~1.85 because of the lower mode can be shifted mainly.
Next, a wideband rhombus-like planar slot antenna with an offset microstrip feed line are proposed and experimentally studied. By varying the angle at the right part of this rhombus-like slot and selecting the proper offset distance, it is found that the impedance bandwidth of the proposed antenna can be enhanced. In order to improve antenna’s bandwidth, another proposed slot antenna with the combination of square-ring and rhombus slots is proposed. In this design, the fundamental mode of rhombus slot and the higher mode of square-ring slot are excited simultaneously. Then the antenna size would not be influenced. From studied results in those slot antenna, it is found that the performance of the cross-polarization levels radiation patterns is not good because of the use of wide slot. In order to reduce the cross-polarization levels, a rhombus slot antenna enclosed by a square-ring slot is proposed. It is seen that cross-polarization levels can be reduced.
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