| Antennas with small VSWR, ommi-directional radiation, small size, simple structure , light weight and low cost ,are very attractive for nowadays communication applications. The planar monopole antenna not only has these merits but also has the properties of wideband, low profile, and easily connecting to microsrtip line feeding network. Therefore, planar monopole antennas satisfy the small size and broadband requirement of today's communication terminal. So, planar monopole antennas attract more and more attentions. In order to widen the band of antennas and get bandstop, this thesis conducts many works based on the analysis of the existing references about monopole antennas. Two new kinds of monopole antennas are proposed, fabricated and measured. The measured results are in well agreement with simulated results. The creative works of this thesis are:1. A new kind of cicular monopole antenna with an eyelet in the center of the radiation is proposed.The resonance performmace is improved by the eyelet and the frequence band of this monopole antenna is wider than that without eyelet. Band-notched characteristics are realized by inserting slots on radiators, so that the antenna can avoid potential interference with some special frequency bands.2.A novel multistep monopole antenna is proposed.Method of multistep feeding is adopted to make sure that the current is continuous at the feeding district and the impedance matching is improved.Both of upon antennas are simulated by numerical software. Furthermore, the circular monopole antenna is fabricated and measured. The theoretical broadband characteristics are verified by the experimental results. The results show that both of the proposed antennas can be used in UWB systems. |
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