Study Of Tropospheric Electromagnetic Wave Over-the-horizon Propagation Based On Parabolic Equation

Wireless communication mainly uses electromagnetic waves to transmit signals.The propagation of electric waves in the troposphere atmosphere requires refraction,diffraction,scattering and absorption.The current communication is not only used in the range of line of sight,but also has a certain demand in the transmission and application of over-the-horizon: in the military,the radar's over-the-horizon detection distance is conducive to the collection of enemy information;in civilian use,super Line-of-sight wave propagation also affects communication between ships.Interference caused by abnormal line-of-sight propagation(mainly atmospheric turbulence scattering)can also have a significant impact on communication system performance.Therefore,it is of great practical significance to study the over-the-horizon propagation of electromagnetic waves in the troposphere.The parabolic equation model is a deterministic wave propagation prediction model derived from the wave equation.The parabolic equation calculates the propagation problem of radio waves in the troposphere.It can simultaneously consider the refraction,scattering,absorption and irregular topography caused by the atmospheric environment,the reflection caused by the surface medium,and the diffraction effect.After the fast Fourier transform,the fast calculation can be performed.Electromagnetic distribution data of the 100-kilometer super-viewing area.Based on the parabolic equation propagation model,the effects of radio wave over-the-horizon propagation in the presence of atmospheric waveguides and atmospheric turbulence are studied.The main research work in this paper is as follows:Firstly,the basic principle of two-dimensional parabolic equation is introduced in detail.The radio wave propagation in free space is simulated and compared with the two-ray model.The correctness of the parabolic equation algorithm is proved.The basic model of the atmospheric waveguide and its corresponding trapping wavelength and trapping angle are studied.In the evaporation waveguide,the electromagnetic wave propagation characteristics of different frequencies and emission sources are studied.It is found that the lower the emission height,the more energy is trapped by the atmospheric waveguide;the atmospheric structure in the actual atmospheric environment is characterized by uneven distribution.Considering the different refractive index profiles at different locations,the difference distance algorithm is used to fill the intermediate distance position to construct the non-uniform waveguide structure.The distribution of the over-the-horizon effect in the 15 km fault of the evaporating waveguide is analyzed,and the distribution of the detectable area and the detection blind area is studied.Characteristics;combined with digital maps to simulate the over-the-horizon propagation of suspended waveguides with terrain barriers;and considering the water vapor density and humidity in the marine environment,water and gas absorption has an important impact on the transmission of over-the-horizon,providing radar detection A certain guiding basis.Secondly,based on the quasi-three-dimensional parabolic equation method,this paper uses the two-dimensional parabolic equation to quickly simulate the propagation of electric waves in three-dimensional space.Consider the influence of meteorological parameters such as temperature,humidity and wind speed on atmospheric turbulence,and the influence of atmospheric terrain model of complex terrain and microwave band on turbulent over-the-horizon propagation.Based on the comparison of the scattering model of PE and MOM and literature test data,the correctness of the proposed algorithm is proved.The model is used to predict the atmospheric turbulent scattering over-the-horizon propagation over a certain terrain in the United States(W93.57 – W95.64,N30.68-N32.68).The results show that the turbulence vs.path loss in the line-of-sight region The impact is small.In the over-the-horizon area,electromagnetic scattering caused by atmospheric turbulence significantly affects the signal receiving level,resulting in over-the-horizon.With the increase of the propagation distance,the multipath effect of the electric wave tends to be obvious,and the amplitude of the field strength along the propagation direction appears random fluctuations;the atmospheric scattering effect decreases with the increase of the height,which mainly affects the low-altitude position at a long distance;The over-the-horizon effect of scattering decreases with the increase of the frequency of the electric wave;the influence of atmospheric turbulence on the transmission of the atmospheric waveguide is relatively small,which only affects part of the leakage of the atmospheric waveguide.