Study Of Radar Detection Performance In Evaporation Duct

Evaporation duct is a special kind of surface duct which is usually occurred in the marine environments. It is due to the evaporation of sea water makes the sea within a limited scope with a high degree of humidity in the atmosphere and the sharp drop in the sea to form a sea-surface duct. The evaporation duct can trap part of the the electromagnetic waves in a certain thickness of the atmosphere. As a result, the propagation characteristics are changed and the electromagnetic waves generated abnormal phenomenon spread .The features of evaporation duct may be applied in electronic equipments such as radar, communication and ECM ,etc. It have a serious impact on the wireless devices which work at the sea . For the example of the radar ,because of the evaporation duct's existence it may occur over-the-horizon radar detection, also it may occur the radar blind spots and other issues. Therefore, to carry out the rearch on the radio propagation characteristics of evaporation duct environment and its application to explore the theory is of great significance and value of the military.This article first describes the atmosphere to form the waveguide properties of the environment, the parameters and characteristics of the wave-guide for the dissemination of electromagnetic waves. Due to evaporation duct is a special atmospheric duct, the article analyse the evaporation duct's forecasting model and modified refractivity profile on the basis of an analysis of the atmospheric duct. Through analyzing the Helmholtz equation, the parabolic equation is got, which is satisfied with the electromagnetic wave under inhomogenous distribution of atmospheric refractive index.The Fourier split-step method provides the solution of the parabolic equation. As a result we receive the electromagnetic wave transmission loss formula in the environment of evaporation duct. On the condition of given parts of parameters, the article have calculated the electromagnetic wave propagation loss. Also compared the electromagnetic wave transmission loss between the standard atmospheric environment and the evaporation duct environment. Based on radar theory the article analyse the radar detection performance assessment model. Using the pattern the article calculated the maximum range of a radar and analysed the factors which impact the the maximum range of a radar. Finally, in connection with concrete radar parameters, effects of ducts on radar range and detection performance are calculated ,simulated and discussed. The results obtained are of great value for the overall design of radar systems. Also analysed the characteristics of the sea clutter, simulated and calculated the sea clutter's impact on the probability of the radar. This paper studies of sea clutter radar detection performance impact of providing the basis and reference.