Research On Space-Time Anti-Mainlobe Interference Method Of Secondary Radar Based On Circular Array

Secondary radars play an important role in modern military and civilian fields.The civil air traffic control secondary surveillance radar provides an important source of information for airport aviation control,route surveillance,and environmental perception.In the military,secondary radar based electronic reconnaissance has become an important part of electronic countermeasures,and it occupies a pivotal position in modern electronic warfare(EW).With the increasing complexity of the working environment,various types of electromagnetic interference make the application of secondary radars face new challenges.Especially the interference located in the direction of the main lobe has become an important factor that affects the analysis of secondary radar signals and restricts the application of secondary radars in complex electromagnetic environments.However,at present,the existing air-domain main lobe anti-jamming methods cannot solve the problem of interference suppression when the desired signal and the interference are in the same direction,the suppression method for the main lobe interference of the secondary radar has not been fully studied.Aiming at the problem of high signal analysis error rate of secondary radar under strong main lobe interference,this thesis mainly studies the technology and method of secondary radar main lobe interference suppression based on spread spectrum communication technology.Moreover,the blocking matrix preprocessing(BMP)algorithm for the uniform circular array model in the space-time domain is firstly derived,which enables the suppression of the main lobe interference under the secondary radar space-time model to be realized.The main research contents include:1.Introduce the basic knowledge of secondary radar anti-jamming.Firstly,the working principle and signal model of the secondary radar are briefly explained;secondly,the array model of the uniform circular array in the airspace is mathematically modeled,and the traditional beamforming anti-jamming method in the airspace is introduced;Two preprocessing algorithms of feature projection and blocking matrix are studied However,these two methods have the problem of main lobe beam offset,and when the main lobe interference is in the same direction as the desired signal,the effective suppression of the main lobe interference cannot be achieved.2.Aiming at theabove problems,a method to improve the interference suppression of the main lobe of the circular array through space-time two-dimensional processing is proposed.Firstly,a space-time two-dimensional uniform circular array model is established,and the space-time LCMV algorithm and the space-time feature projection matrix preprocessing algorithm are introduced.Secondly,the blocking matrix preprocessing algorithm is extended from the space domain to the space-time domain,and the blocking matrix of the circular array model under space-time processing is deduced;the theoretical analysis of the proposed algorithm is carried out to verify the effectiveness of the proposed method.Aiming at the problem of beam pointing deviation in the pre-processing algorithm,four methods of directional pattern conformation are introduced.Finally,according to different scenarios and application conditions,the three space-time anti-jamming methods are respectively subjected to directional pattern simulation experiments.The simulations show that when the main lobe interference approaches the desired signal from the space and time domains at the same time,the main lobe of the characteristic projection matrix algorithm and the spacetime LCMV algorithm will be deformed,and the space-time blocking matrix preprocessing algorithm in this thesis can effectively suppress the main lobe interference and reduce the gain loss of the desired signal.3.The space-time two-dimensional blocking matrix preprocessing algorithm under the circular array model derived in this thesis is applied to the secondary radar interrogator scene with main lobe interference.Simulation experiments and performance analysis of the derived algorithm are carried out in terms of performance indicators such as bit error rate,the output signal to interference noise ratio and signal to interference noise ratio improvement.Simulation shows that the algorithm in this paper can significantly increase the output SINR and reduce the bit error rate,and obtain a higher output signal-to-interference and noise ratio,and reduce the bit error rate of signal analysis.