| Evaporation ducts, or tropospheric ducts in general, can guide radio waves to distances far beyond the horizon with less attenuation, and then severely impair some certain radio wave system. Because of radio wave propagating along the ducts with enhanced fields on the order of the free-space field, the problems of the co-channel interference are more complicate for communication systems with the results of intersystem interference and the formation of other system, and therefore affecting the determination of the coordination distances or the optimization of the distribution and separation of delay, and for surveillance system such as radar system the problems can be radar holes or the extensions of detect range. All of these problems can be fatal to certain appliances especially to attack and defense system. It is concluded from the investigations that evaporation duct propagations and other tropospheric duct propagations become very complicate multi-discipline problems at present time including EM theory, atmospheric science and applied science etc., and one of the tough and hot issues in the field of tropospheric propagation. In China, the solutions of duct propagation are so short that the active demand can not be met for defense such as the prediction model for evaporation duct environment. So the researches on the characteristics of evaporation duct environment, propagation and its applications have great theoretical significance and are of great value to military.According to state-of-the-art of evaporation duct propagation research, and to meet the demands on the prediction techniques of evaporation duct environment and the assessment of radar performance under evaporation duct environment, this dissertation gives a thorough research in depth on the subject described above. The researches include the prediction theory of evaporation duct and its applications, the theory of ray tracing based on which the prediction of radio wave rays are conducted and its application to the predicting of radar range performance under a given evaporation duct, and the characteristics of tropospheric ducts over China.The conclusions derived from these investigations are following:First, the theoretical prediction method of evaporation duct brought forward in this dissertation is successful. According to the results of the field test, the accuracy of this method in predicting the occurrence of evaporation duct arrives at 80%, the error of the average predicted evaporation duct height is about 28% with each error ranging from 24.6% to 57.6% within the measurement height range. All of these results along with similar research results show this theory is feasible and practical.Secondly, the resolution of ray tracing based on the differential equations avoids the limitations of the methods based on integral equations such as low computation efficiency and the calculation difficulty at small initial angles in the vicinity of antenna, and the higher computation precision remains with a higher efficiency. The results show that the apparent radar range corresponding to the real height agrees with the published results within 1%, and the computation time of thismethod is in order of sub-milliseconds to determinate a pair of range and height using desk computer at present time.Thirdly, the conclusions of the two aspect applications are given as follows:The exploration of the application of the evaporation duct prediction to the flux relationship research and evaporation duct predicting shows that based on this predicting method and with microwave refractometer, as sensor, (1) the dimensionless gradient function of temperature, humidity and refractivity in the flux relationships can be determined with higher precision, (2) the limitations of conventional observations on the predicting accuracy for evaporation duct can be avoided and the precise prediction for evaporation duct can be obtained with the accurate measurement of refractivity profile within a few meters.The radar performance under given evaporation...
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