Theoretical Research On Target Stealth Based On Coherent Acoustic Perturbation Of Evaporation Duct

Evaporative duct is a common atmospheric phenomenon with abnormal distribution of refractive index on the sea surface.It is widely used in maritime communication and detection.Evaporative duct over-the-horizon radar poses a great threat to the free navigation of ships and other targets on the sea surface.The study of stealth technology for evaporative duct over-the-horizon radar is of great significance for improving the survivability and strike capability of military targets such as ships.Starting from the transmission channel of the over-the-horizon radar,this paper applies the theory of coherent acoustic disturbance to the atmospheric refractive index in the evaporative duct environment.Combined with the parabolic equation method,the influence of acoustic disturbance on the radar detection performance is studied.The main research contents of this paper are as follows:Based on Debye’s theory,the relationship between radio wave propagation and atmospheric refractive index and modified refractive index is discussed.The reasons for the formation of atmospheric ducts and the distribution of refractive index in atmospheric duct are analyzed.According to the principle of geometric optics,the theorem of refraction under spherical layered atmosphere is deduced,and the basic theory of ray tracing is obtained.The parameter conditions required for the formation of the evaporation duct and the necessary conditions for the transmission of electromagnetic waves in the evaporation duct are studied.Starting from the basic theory of acoustics,the basic laws of sound waves propagating in the atmosphere are studied.According to the superposition principle of acoustic waves,the superposition of different acoustic waves is discussed.Based on the actual situation of acoustic wave propagation,the attenuation of acoustic waves in the atmosphere is described in macroscopic and microscopic aspects.Starting from the gas state quantity that affects the atmospheric refractive index,the relationship between the acoustic pressure and the atmospheric refractive index is studied,and the feasibility of coherent acoustic waves perturbing the evaporation duct is analyzed.A spherical acoustic source array is set up,and the far-field approximation method and the superposition principle method are used to simulate the atmospheric refractive index distribution under the influence of acoustic disturbance.The parabolic equation method for evaluating the radar detection performance in the evaporation duct environment is studied.The origin of the parabolic equation,the setting of boundary conditions,and the calculation of transmission loss are introduced.The finite difference method is used to solve the parabolic equation.The Propagation loss distribution of the radar in different ducts environments is simulated,and the detectable range and blind area of the radar are analyzed.The influencing factors of acoustic disturbance stealth are analyzed,different acoustic source arrays are set up,and the influence of acoustic source spacing,relative position of acoustic source and electromagnetic wave frequency on radar detection is studied.The experimental results show that the smaller the distance between acoustic sources,the higher the frequency of electromagnetic waves,the greater the influence of acoustic wave disturbance on radar detection,and the effect of the relative position of acoustic source on the maximum detection distance of radar is random.In this paper,it is found that the target stealth method of coherent acoustic wave perturbation evaporation duct is feasible,but also has instability.The acoustic disturbance stealth theory for evaporation duct over-the-horizon radar studied in this paper has certain guiding significance for the development of new stealth technology,and has potential application value in sea communication and military.