Distributed Over-the-horizon TDOA Technology Based On Tropospheric Scatter Propagation

Electronic reconnaissance is the "clairvoyant" in modern electronic information warfare systems,which provides important parameters for obtaining combat intelligence by capturing the geographic location of radiation sources.However,in the distributed groundbased monitoring system,the complex geographical environment of the earth’s surface will have different degrees of influence on the target radiation signal,so it has been difficult to break through the long-distance non-direct-sighted target positioning.Considering that troposcatter communication has the advantages of large transmission capacity,covering the curvature of the earth,not easy to be detected and interfered,and the propagation medium is less affected by nuclear explosions,this special meteorological condition can be used to complete long-distance communication of signals.However,it is very difficult to accurately analyze the propagation path of the signal in the troposphere and the changes in the real environment.Therefore,this paper proposes a distributed over-the-horizon time difference positioning method based on troposcatter propagation,which can not only make up for the shortcomings of the existing troposcatter path model and atmospheric waveguide path model,but also judge the channel type of the ground monitoring station to receive the target signal.,so as to achieve accurate positioning of long-distance targets.The main research results of this paper are as follows:1.Aiming at the complicated situation of electromagnetic wave propagation trajectories in troposcatter scattering,the calculation method of the height of the scattering point in the troposphere is derived by using the ray tracing method and the geometric method,and then combined with the equivalent earth radius method to calculate the long-distance propagation signal path.In the construction of the equivalent earth radius model,the atmospheric refractive index is judged with the different heights of the scattering points,and the earth radius is locally equivalent in combination with different climatic environments,so as to calculate the tropospheric scattering propagation path that conforms to the actual environment.2.The atmospheric ducting phenomenon is considered as a special case of troposcatter scattering and is also considered in long-distance target positioning scenarios.Using the average height of the waveguide layer as the earth radius compensation value,the propagation path of the electromagnetic wave continuously refracted in the waveguide layer is equivalent to the arc length between the transmitting end and the receiving end,and the earth radius compensation method is used to calculate the electromagnetic wave in the atmospheric waveguide channel.propagation path.3.Since the antenna elevation angle of the target radiated signal cannot be judged in the actual environment,the channel type of the received signal cannot be judged.Therefore,according to the propagation mode of the long-distance received signal,a variety of propagation scenarios are simulated,and the received signal is analyzed by using the positioning equations of different propagation modes.In this way,it can be effectively determined which channel the ground monitoring station receives the signal through in this scenario.Based on the proposed positioning model,this paper simulates and analyzes the longdistance target positioning performance under different scenarios and measurement errors.The simulation results show that the channel determination method proposed in this paper can accurately determine the channel type of the received signal,and the analysis results of the corresponding positioning equations in different scenarios have optimal positioning performance,enabling accurate positioning of long-distance targets.