| In recent years, with the rapid development of wireless communication systems, especially mobile communications and WLAN applications, the antenna as a wireless transmitter and receiver terminal is proposed new requirements. On the one hand, with the increase of antenna in quantity and frequency extending, antenna is required to achieve effective coverage and to be good electromagnetic compatibility. Otherwise, the interference between antennas in limited space is more serious, which will affect the quality of communication. On the other hand, in receiver terminal, the antenna is required to work in multi-band and has small feature. Therefore, the Anti-interference broadband antenna and multi-band miniaturization antenna are becoming important research topics.Based on the above requirements, broadband directional antenna with good electromagnetic compatibility characteristics is proposed firstly in this paper. Through loading technology to realize the H surface directional of conical antenna. Moreover, the thesis is mainly on the topic of miniaturization and broadband characteristics for WLAN antenna. Small multi-band antennas on the basis of broadband planar antenna are designed through deformation and improvement, and the related theory and technology is studied. Content and innovation in the dissertation are as follows:(1) A novel broadband loaded biconical antenna is designed firstly to realize directional radiation pattern in H-plane. The shorted biconical antenna retains the characteristics of wide3dB bandwidth to achieve effective coverage, and, it can solve the problem of Electromagnetic interference between antennas for its directional. Aim minimal radiation direction of the antenna at interference source to realize anti-interference.(2) To expand frequency band and reduce antenna size as much as possible, a novel broadband loaded mono-cone antenna is designed firstly to realize directional radiation pattern in H-plane. Omni-directional cone antenna is made improvement by adding shorted stub to avoid electromagnetic interference sources. The3dB beamwidth in H-plane is wide and the return loss is less than-10dB within the frequency range of1.7-6.0GHz of this antenna. The acceptable agreement of measured and simulated results shows the kind of antenna has perfect pattern properties and input impedance.(3) Based on FDTD, a novel broadband planar antenna with a bevel for WLAN2.4GHz has been improved by adding Short patch and parasitic elements. Two parasitic elements at the top of the antenna can not increase the height of antenna and can widen bandwidth. The loading broadband planar antenna is good omnidirectional in horizontal plane whose ripple is about2dB.The improved antenna is designed, simulated and verified.(4) An improved broadband planar antenna with L-type slots in parasitic elements is presented. Compared with conventional planar antenna, this antenna can produce wider frequency bandwidth. It can be concluded from the good results of VSWR<2at2.3-2.57/5.14-5.44GHz, which could cover the WLAN dual-band of2.4-2.484/5.15-5.35GHz. This antenna is good omnidirectional in horizontal plane whose ripple is less than3dB.(5) A novel shorted broadband planar antenna with L-type slot in the Vertical radiation element is proposed in the paper. The antenna could cover WLAN multi-band. It can be concluded from the good results of VSWR<2at2.3-2.52/5.12-5.86GHz, which could cover the working bands of IEEE802.11a/b/g2.4/5.2/5.8GHz (2.4-2.484/5.15-5.35/5.725-5.825GHz). Both simulated and measured results show that the proposed antenna is of good application potential in WLAN system. All WLAN antennas presented here have advantages of compact, omni-directional, low-cost, ease of processing and so on. The results show that the anti-interference conical antenna and loaded broadband planar antenna for WLAN have great potential in practical application. |
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