| 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 antennas not only have these merits but also have the properties of wideband, low profile, and easily connecting to microstrip 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 get smaller size antennas and further improve the bandwidth, this thesis conducts many works based on the analysis of the existing references about planar monopole antennas. Two new kinds of planar monopole antennas are proposed, fabricated, and measured. The measured results are in well agreement with the simulated results. The creative works of this thesis are:1. A new kind of planar monopole antennas with slot cut in the radiation patch is put forward. The resonance performance is improved by the slot and frequency band of this planar monopole antenna is wider than that without slot. The effects of ground plate size on the antenna property are studied. The bandwidth of the rectangular planar monopole antennas can be expanded by adjusting the size and location of the ground plate.2. A new kind of ultra-wideband circular planar monopole antenna with circular arc slot cut in the ground plate is put forward. The resonance performance of this kind of antenna is improved significantly by the circular arc slot. The size of this kind ofantenna is further reduced and the bandwidth is further expanded.The proposed antennas are fabricated and measured. The theoretical broadbandcharacteristics are evidenced by the experimental results. The results show that these methods can be used to improve the performance of the planar monopole antennas effectively, the size of the planar monopole antennas can be further reduced and the bandwidth can be further enlarged. |
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