.vhf / Uhf Airborne Broadband Antenna Miniaturization

Due to the potential applications of frequency-hopping and spread-spectrum techniques in the modern military secure communication systems, the development of broadband omni-directional miniaturized VHF/UHF antennas, which are known as key components of the communication systems, is an urgent and important issue in theory and applications. Being associated with the research project"Miniature of Broadband Airborne VHF/UHF antenna", this thesis is mainly concerned with the optimal design of the antennas which operate at VHF/UHF frequency band respectively. The major contributions of this thesis are outlined as follows:1.The frequency bandwidth extension method and antennas miniaturization technology of wire antennas and planar monopole antennas are summarized briefly in this thesis. Besides, their current developments are reviewed. These summarizations provide the basis of VHF/UHF antennas design.2.In order to get the miniature and broadband antennas which meet the directional pattern, VSWR and gain requirements, the thesis uses rationally the theoretical results of antenna miniaturization and bandwidth extension. Besides, using genetic optimization, the folded monopole antenna is studied. The height of the folded antenna designed in this thesis is only 0.09λmax, which sharply reduced the antenna size.3.From the cone-wideband antenna characteristics, the use of wide-angle triangle structure extends the bandwidth of the antenna. Finally, get the angle of wide-angle triangle structure which can gain the optimal antenna.4.Designed a new type of antenna structure using gap and arm loading. The antenna not only significantly extends the antenna bandwidth, but also reduces the antenna size. The designed antenna reduced the size by half compared with the original antenna.5.The summary of the whole thesis is given and some possible key techniques of the antenna design are predicted.