Radio Propagation Path Loss In The Woods

Because environment is the main influencing factor of propagation and mobile communication has been universally used in city region since 1990s, many scholars had focused on the study of signal attenuation between the streets and buildings. At present, it has been studied very successful. Mobile communication has also been universally used in rural area and suburb since 2000s. The character of the rural area is there are many trees and crops. The effect of trees and crops on electric-wave propagation has been a new thesis for communication engineers.Through studied the former thesis on electric-wave propagation in forests, the signals attenuation has been studied in this paper about small and large area forests. As for the small forest, the electric fields of receiver point mainly come from the correlation fields. At first, the relativity dielectric constant ε_r is acquired by using the experiment. The electric field expression of receiver point is calculated by using scatter theory in the random and electromagnetic field theory. The expression of attention constant, the mathematic model, is calculated. The parameters of usual kind of trees are measured through experiment, and they are substituted into the mathematic model and are calculated. The results of calculation are compared with the results of measure and a good agreement in each case is found better. As for the large forest, the scatter fields mainly come from the non-correlation fields. It is very difficult to analyse and calculate by using the scatter theory, so the ensemble of discrete scatterers can be replaced by an equivalent continuous medium described by an effective dyadic permittivity ε .The expression of electromagnetic was derived by using the saddle point method, Hertz vector potential function and boundary condition. In order to make the results of calculation in accord with the actual case, different kind of tree is calculated by using the different ε based the literature, and the results of the path loss of radio wave propagation following with the variety of frequency,distance and dyadic polarization quotiety are derived by using Matlab. The results of calculation are compared with the results of measure and a good agreement in each case is also found better.The main purpose of this thesis is giving a simple model and analysis method for calculating and analyzing the attenuation while radio wave propagation pass through the forest. The thesis provide the theory functions for the station address choice of mobile communication and the signal evaluation of the communication and electronic-war army in manoeuvre and battle.The content of this thesis including the following five chapters: The first chapter describes the importance and the background of study electric-wave propagation path loss, the study method and the content of this thesis; the second chapter describes the base knowledge of electric-wave propagation path loss. The propagation of plane electric-wave, the propagation and scattering in random medium and the method of math physics are introduced in this chapter. The third chapter and the fourth chapter are the main content of this thesis. The path loss of the small and large forest is respectively calculated and analyzed while radio wave propagation pass through the forest.In the fifth chapter, the study of electro-wave propagation is summarized and the development prospect electro-wave propagation is introduced.The study content of electro-wave propagation path loss in canopy is very plenty. Because the time of study is limited, the thesis only studies the path loss in small area forest and large area forest and can not study the path loss in the crops and meadows. If the ideal effect model of calculating electro-wave propagation path loss in canopy can be achieved, it needs much more comprehensive study.