Study On Electromagnetic Wave Propagation Parabolic Equation Method In Tropospheric Atmosphere

The height of the tropospheric atmosphere is less than 17-kilometer normally and most of the electromagnetic wave propagation happened in the troposphere. Influence of the tropospheric atmosphere on electromagnetic wave propagation are manifold, such as wave scattering, refraction, diffraction propagation effects. Tropospheric duct is formed under unusual atmospheric structure. Its appearance becomes the major factors affecting the electromagnetic wave propagation in the troposphere. China’s territorial waters and coastal areas are in the regions with a high troposphere duct happening incidence. Tropospheric duct have a significant impact on communication of the ship and coast radar. So conducting research on characteristic of electromagnetic wave under the troposphere duct circumstance have practical applications and national defense significance.This paper introduced the formation conditions, refractive index profile models, as well as distribution areas of evaporation duct, non base layer surface duct, containing base layer surface duct, dangling duct and hybrid duct. Then, narrow-angle parabolic equation was gradually derived from the Helmholtz wave equation and then the equation was solved using the split-step Fourier method. After that, narrow angle parabolic equation was used to calculate the electromagnetic wave propagation attenuation distribution in the standard atmosphere and the five ducts structure. This paper also analysised the influence of the atmospheric temperature, humidity on the atmospheric refractive index gradient and the influence of water dielectric constant on the radio wave propagation loss. Results showed that relative air humidity had biggest impact on the atmospheric refractive index and the influence of water dielectric constant on electromagnetic wave propagation loss could be neglected.In addition, this paper also analyzed the main error which was caused in narrow-angle parabolic equation solving process and the quantitative expression of relative error on importing factor was established. Then, how to choose the step according to frequency within a certain precision was also studied. It could maximize the calculation step, there for reducing the computational complexity and improving efficiency within a certain margin of error which was important for real-time performance of the system.