| With the increasing complexity of the electromagnetic environment,multi-type and stronggain main-lobe jamming poses a serious threat to phased array radar,and anti-main lobe jamming technology has become a current research focus.Most of the existing main-lobe jamming suppression algorithms are aimed at specific types of main-lobe jamming environments without making accurate distinctions between the types of jamming.When the radar faces the unknown main-lobe jamming,it is impossible to schedule the optimal antijamming method according to the jamming environment in real time.Therefore,this paper studies the adaptive anti-main lobe jamming method of phased array radar based on jamming identification through theoretical derivation,simulation and measured data under different types of main-lobe jamming scenarios.Based on the modeling of suppressed main-lobe jamming and deceptive main-lobe jamming,this paper firstly simulates and analyzes the specific effects of different main-lobe jamming signals on the beamforming of phased array radar.Then,around the mathematical model of blind source separation(BSS),its basic principle and several typical algorithms are elaborated,which lays a theoretical foundation for the study of anti-main lobe jamming methods in the space-time domain.In terms of jamming identification,the signal characteristic parameters are extracted to accurately identify the jamming type based on the two main-lobe jamming models mentioned above,which provides a priori information for the subsequent targeted suppression of main-lobe jamming.For the suppression of main-lobe jamming,this paper takes the space-domain adversarial algorithm and the space-time domain adversarial algorithm as the entry point to carry out the research.The spatial domain algorithm takes blocking matrix preprocessing(BMP)and eigen-projection matrix preprocessing(EMP)as the research objects,and the suppression mechanism and applicable conditions of these two methods are analyzed by the array pattern and anti-jamming output.For the main peak shift and side lobe level increase caused by BMP,the main-lobe jamming suppression algorithm by BMP preprocessing and similarity L2 norm constraint(BMP-SL2)is proposed.The simulation results show that the BMP-SL2 algorithm has good shape retention and better anti-jamming performance.In the space-time domain,the blind source separation anti-main lobe jamming method based on the beam domain is studied.Through the theoretical derivation of the existing algorithms joint approximation diagonalization of eigen matrices(JADE)and fast fixed-point independent component analysis(Fast-ICA),a main-lobe jamming suppression algorithm based on eqivariant adaptive separation via independence(EASI)is proposed.Considering the problem that the steady-state error and the convergence speed cannot be taken into account in the fixed step size EASI algorithm,an improved EASI algorithm with adaptive step size is proposed.The simulation results show that EASI algorithms have stronger anti-jamming ability.Compared with the fixed-step EASI algorithm,the improved EASI algorithm has significantly faster convergence speed and more stable anti-jamming output.In this paper,two sets of measured data are used to conduct experimental analysis on the spatial and spatial-temporal algorithms to verify the correctness and effectiveness of the theoretical research.It also summarizes the advantages,disadvantages and applicable scope of each main-lobe jamming suppression algorithm,then summarizes and refines the space and space-time countermeasures for different main-lobe jamming types.On this basis,an adaptive anti-jamming method based on jamming identification is studied.After identifying the main-lobe jamming type,a targeted anti-jamming strategy is formed according to the performance advantages of each algorithm,so as to more effectively schedule anti-jamming resources and improve the survivability of the radar under the background of complex mainlobe jamming. |
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