| The research on modeling mechanism and characteristics of ground-sea clutter under the condition of moving radar platform has important theoretical significance and application prospect in clutter suppression,precision strike,etc.however,the echo characteristics and the range-Dopler characteristics of dynamic beam irradiating on the surface of the earth and the sea have not been fully considered in previous studies.Therefore,this paper focuses on the time-varying sea surface and real ground scene under the consideration of dynamic antenna beam irradiation,and at the same time,combined with the near-field SBR algorithm,establishes the electromagnetic scattering model of rough surface under dynamic beam irradiation,the correctness of the method is verified in the theoretical and experimental dimensions,and the high-resolution modeling of the ground-sea clutter is realized by dividing the scattering units,and the space-time characteristics of the ground-sea clutter under different moving conditions of the radar and the environment are calculated and analyzed,it provides a theoretical basis for radar seeker design and environment clutter suppression.The main research of this paper is as follows:Firstly,to solve the problem of geometric modeling of a rough surface under dynamic irradiation with antenna beam,an integrated dynamic geometric model of the beamenvironment is created by combining the motion characteristics of the radar beam with a real refined model of earth’s surface and a time-varying sea surface model.The law of dynamic change of the field of view during the movement of the radar platform of side and oblique view has been established.A linear filtering method combined with time-harmonics is used to create a time-varying sea surface model,and a digital height map combined with a midpoint displacement method is introduced to create a shallow water model.By combining the geometric relationship between the radar platform and the Mediterranean Sea background grid with the antenna pattern,one can obtain the distribution of the incident electric field strength on the background grid when irradiated by the radar beam.In combination with the law of motion of the radar platform,the dynamic change in the distribution of the incident electric field strength is implemented in the Stop and Look form,which provides support for the calculation of the electromagnetic scattering echo in the nearfield.Secondly,to solve the problem of the near-field detection data acquisition accuracy under dynamic beam irradiation,the near-field reflected beam algorithm is applied to a rough surface irradiated by antenna beam,and the darkroom electromagnetic scattering measurements in a dark room are being carried out.The definition of the near-field radiation by antenna beam in the Mediterranean Sea environment is presented,and a dynamic nearfield SBR model is created.The accuracy and feasibility of the algorithm are illustrated by comparison with the exact numerical results of typical target models.Two kinds of rough surface models are built in the darkroom,and the geometric mesh model and the permittivity of the rough sand surface are collected respectively.The playback condition parameters are substituted into the near-field ray algorithm.The simulation results are compared with the measurement results.Thirdly,to study the pattern of changes in the intensity of the echo signal and Doppler frequency shift under multi-scene beam irradiation.Based on a dynamic near-field SBR model,time series of land/sea interference are calculated and analyzed for various radar motion states and land/sea surface parameters,and then a Doppler spectrum is obtained using a Fourier transform.The echo intensities of the static sea surface and the dynamic sea surface at different times are simulated by irradiating by the side-scan and the oblique-scan antennas,respectively.It can be seen from the simulation results that the change in echo intensity over time is highly related to the state of motion of the radar,the mode of beam emission,and the speed and direction of the wind on the sea surface.At the same time,the Doppler spectral shift basically agrees with the theory.The results are of great importance for progress in the study of the echo characteristics of the Mediterranean Sea under irradiation exposure.Finally,in order to analyze the characteristics of land/sea reflections withhighresolution,this article examines the intensity of regional echo under beam irradiation and calculates the distribution of far range-Doppler clutter.The area radiated by the antenna beam is divided by the areas of the unit stray bands,and the local echo intensity is calculated by integrating each small unit.The distribution of clutter intensity is obtained,and the spectrum of range-Doppler clutter is calculated using Fourier transform.The results show that the Doppler shift in different areas of radiation is clearly different,which is closely related to the state of motion of the radar and surface parameters.This lays the theoretical foundation for improving the accuracy of target detection in the conditions of combat operations on mobile objects. |
