Analysis On Marine Duct Propagation Experiment And Investigation On The Modal Theory

Atmospheric duct propagation is an anomalous propagation phenomena associated with specific weather conditions. When atmospheric duct exists, if the electromagnetic wave transmitter located in the duct layer, the electromagnetic wave launched with the angle smaller than the critical angle and with smaller wavelength than the maximum trapping wavelength is traped in the duct layer and duct propagation forms. Atmospheric duct can increase the error of radar ranging, direction finding and velocity measuring, enhance radar clutter, extend detection range and enlarge the detective blind zone. The effect of atmospheric duct indicates wide application in communication. So it is very important to reserch the enviroment characteristics, propagation characteristics and applications of atmospheric duct.Firstly, the effects of space environment on communication are discribed, with emphasis on atmospheric duct phenomenon including the meteorological conditions, structures, characteristics, basic conditions of atmosphere duct propagation and a summary on atmospheric duct distribution over China. In addition, its impacts on detection and communication system and measures to mitigate the influences are given. Secondly, as an emphasis, a marine duct propagation experiment is analyzed in detail. This thesis discusses the basic form of electromagnetic wave propagation, loss mechanism and calculation about propagation distance,and generalises loss regular of wave propagtation. analyses experimental datas integrating loss mechanism, the factor impacting on experimental datas in terms of experimental circumstance. Finally, to get distribution of the electro-magnetic field intensity on the arbitrary point in space, investigate the mode theory, deduce it detailedly in theory, represent its key algorithm, and present the results of wave propagtation loss with mode theory. The results verify trapping function that the duct induce to wave.