Research On Semi-empirical Wave Propagation Model On Large Scale Terrain And Application In Radar Site

The modeling of the propagation of electromagnetic wave is one of important issues in the study of electromagnetic engineering.A good propagation model is of high application value,which will benefit the communication and national defense.The current propagation models are divided into empirical propagation models,ray-tracing models and parabolic equation models.The first ones are approximative,multitudinous and efficient.The others are accurate,universal and consume lots of computing resources.It's hard to improve computational efficiency only by improving hardware performance,and empirical models are the key to solve electromagnetic wave propagation problems in large scale scenes.Beginning with classic models,micro-cellular propagation models and macro-cellular propagation models are studied,which will be used to help to solve radar-siting problems.The main works of this dissertation include:(1)Based on propagation mechanism of electromagnetic wave,the gain of effective antenna height and diffraction loss calculation of more than 2 peaks are the focuses.Using GTD(Geometrical Theory of Diffraction),the problem,that the deficiency of correction term of computational formula about diffraction loss calculation of more than 2 peaks,is solved.And this will be used in the latter study.(2)The propagation models of electromagnetic wave in urban environment are studied.The mechanism and concrete realization of Okumura-Hata model,WI model and Lee micro-cellular model are studied,which represent city model with no geometrical information about buildings,regular city model and irregular city model respectively.they are proven effective by examples.In the end,the advantages and disadvantages of the 3 models are analyzed.(3)Propagation models on large scale irregular terrain are studied.The mechanism and concrete realization of Lee macro-cellular model is studied,whose precision can be improved by measured data.The precision of calculation of diffraction loss can be improved by measured data.The classical model,named ITM,is also studied carefully.the advantages and disadvantages of the 2 models is analyzed by calculating the same example.(4)Finally,aiming at the demand of radar siting,the software prototype,which is similar to RPAS(Radar Position Analysis System)used by US army,is accomplished,using previous models,which the calculation of CNR(Clutter-Noise-Ratio)is added.