A Practical Method Of Electromagnetic Situation Assessment In Complex Terrain Environment

Electromagnetic situation prediction has an important research value in the field of military civilian communication,electronic countermeasure,Location Investigation of interference source and so on.The accurate,efficient and practical electromagnetic situation prediction technique is of great significance to the development of field mentioned above.At present,various empirical and semi empirical model can only be used to estimate the channel link margin under the certain environment and cannot be used for accurately assessing electromagnetic situation.Accuracy model represented by ray tracing method can accurately calculate the field strength,but its heavy computation and the full path GIS demand constraint the practical application of this kind of method,so it cannot meet the engineering application requirement of field strength prediction in complex environment.In this paper,an accurate,efficient and practical electromagnetic situation assessment method is proposed to solve the problem of accurately evaluating the electromagnetic situation without the help of GIS.The following are the main contents of this paper.Classify the shape of static terrain and ground objects in the aspect of radio wave propagation,the requirement of electromagnetic situation for geometric characteristics of ground object is analyzed and the geometric characteristics of the static terrain and ground objects boundary are studied and summarized.It lays the geometric foundation for accurate calculation of field strength.Through the simulation analysis of the reflection characteristics of terrain and ground surface with the change of dielectric parameters,we can get it is necessary to measure and calculate the electromagnetic characteristics parameters of a certain terrain in the electromagnetic situation assessment,based on this,this paper proposed vertical transmission method which has powerful maneuverability and is relatively reliable to measure and inverse electromagnetic characteristic parameter of ground object,then determine the propagation coefficient of electromagnetic wave in the boundary of the terrain environment.It lays the foundation of calculating field strength accurately.A new approach for complex environment electromagnetic situation assessment is proposed in this paper,based on the theory of electromagnetic field intensity calculation,the mathematical model of electromagnetic situation assessment method is deduced.In multipath determination,we designated the terrain in the intersection of visual area and beam crossing region as the effective terrain objects.The objects characteristic points are acquired by laser ranging to model the effective objects,and then determine the multipath wave in receiving points according to the ray tracing theory.In terms of field strength calculation,the prediction area is divided into visual areas,and the visual area is divided into direct wave and uniform area.On the basis of obtaining the reference field strength of each direct wave and uniform area by means of certain measuring methods,calculate the direct wave and multipath wave field in every receiving point.Use the mathematical model of electromagnetic situation assessment to calculate the total receiving field at the receiving point.Combination all the visible area of field strength prediction results to get the electromagnetic field distribution.Based on the electromagnetic situation assessment method,we predict the field strength distribution of realistic mountain and construction area scenarios.By comparing the measured results with the predicted results,the validity,accuracy and practicability of the electromagnetic situation assessment method proposed in this paper are verified.