Study On Radio Wave Transmission Loss And Scattering In Vegetation

With the development of wireless communication technology,electromagnetic waves have existed in all aspects of our lives,and the propagation environment is the main factor affecting the propagation of electromagnetic waves.In the 1990 s,the radio communication technology was first used in urban areas,many scholars studied the influence of streets and buildings on the propagation of electric waves.At present,it is relatively mature.Since the 21 st century,the radio communication have also been widely used in suburban and rural areas.Since suburbs and rural areas have extensive vegetation coverage,the research on the propagation of radio waves in vegetation plays an instructive role in the prediction of wireless network.Meanwhile,in military warfare,due to the variability and complexity of the battlefield,it is crucial to ensure the stability electromagnetic wave communications in vegetation environment.So,research on the propagation characteristics of trees and other vegetation has become an important and hot issue.The research in this paper is based on the results of previous researches,the electromagnetic wave band studied is from 0.5 GHz to 60 GHz,and the full text is divided into six chapters.The first chapter introduces the background and status,and describes the main ideas and the content of the paper.The second chapter introduce the basic theory of electromagnetic wave propagation and lays the foundation for subsequent research.The third chapter takes different methods of modeling and calculation according to the size of the vegetation.For small woods,using the principle coherent fields and wave propagation in random media combined with boundary conditions,we can calculate the field intensity expression of the receiving field according to the vector wave equation of the mean filed in the crown,and calculate the scatter amplitude to get the mathematical expression of the final decay constant,and the relationship between the dielecteic constant of trees and the water content of trees is given and the specific method for measuring water content of trees is described.For large patches of wood,the Tmair model is used,mainly considering the role of the side wave,ignoring the influence of the direct wave and reflected wave on the receiving antenna signal,and then briefly introduced the three-layer model and four-layer model,and compared the calculated results with the measured results.In the chapter 4,we introduced the two-ray model and the transmission coefficient of the two-dimensional greenbel,then based on the principle of vector radiation and the idea of ray tracing,this paper discretizes the trees into several points and considers the path experienced by the vegetation in the primary and secondary reflections.Finally,the electric field around a single tree is calculated.In chapter 5,this paper also analyzes and compares some existing theoretical models,according to different locations in the forest where the receiving antenna is located,provides different parameter models,so that the accuracy of the prediction is improved.,and the paper proposes a general model of electric wave propagation in forest vegetation based on radiative energy transfer theory,and what is more,we make a cpmparative analysis of the scope of application and accuracy of each model.The sixth chapter summarizes and analyzes the full text and puts forward the next work plan.The main work of this paper is to use different methods to analyze the effects of vegetation,such as individual trees,greenbelts,small woods and large forests on the propagation of electromagnetic waves.Finally,a general model is proposed for the propagation of electromagnetic waves in vegetation based on the radiative energy transfer therory,and analyzed the scope of application and the advantages and disadvanteges of each method.This paper provides analysis methods and theoretical guidance for the prediction of propagation of radio signals in a comprehensive building environment with vegetation.