Research And Implementation Of Anti-Jamming Algorithm Applied In Beidou Satellite Navigation System

At this stage,the military field has an increasing demand for electromagnetic warfare,and the electromagnetic environment in the civilian field has become increasingly complex.With the successful launch of all Beidou-3 satellites,it marks the success of the construction of my country's Beidou-3 satellite system.Because the Beidou navigation satellite signal has a fixed working frequency band and narrow bandwidth,it is extremely susceptible to a variety of electromagnetic interference.The anti-jamming technology for the receiving end of the Beidou satellite navigation system is an important subject in the Beidou field and the field of antiinterference.When the Beidou signal reaches the ground,the power is weak,much lower than the noise power.After various intentional or unintentional interference,it will cause excessive positioning error or even loss of positioning information.Therefore,this article has conducted theoretical research and hardware implementation for the anti-jamming algorithm applied to the Beidou satellite navigation system.The main tasks are as follows: 1)The development process and research status of the global satellite navigation system are introduced.Especially for the anti-jamming technology of satellite navigation,the research history and current situation at home and abroad are elaborated in detail,and various beamforming algorithms and system-level solutions in the past 20 years are analyzed with emphasis.2)The array signal model of Beidou anti-jamming is given,and the system simulation of signal generation and anti-jamming algorithm is realized.The simulation and comparison of three beamforming criteria,maximum signal-to-interference and noise ratio,minimum mean square error,and linear constraint minimum variance,are proposed.Four optimization algorithms are proposed to solve them and realize adaptive Beidou anti-jamming.Finally,the performance of anti-jamming algorithms in airspace and space-time domain is analyzed.3)Aiming at the problem of solving the optimal weight of the anti-jamming algorithm,an iterative algorithm based on conjugate gradient is proposed,and compared with the steepest descent method and the direct inversion method.The proposed algorithm has faster iteration speed and easy iteration times.The advantages of control and strong beamforming ability.In addition,for the traditional power inversion algorithm for weak interference nulls,the algorithm is optimized,and the array weights are projected into the noise subspace.Finally,the dimension of the algorithm is expanded,and the space-time algorithm can greatly increase the degree of freedom of the array and enable it to filter in the frequency domain.Simulation shows that the algorithm expands the degree of freedom and can filter in two-dimensional space and time domain.4)At this stage,more and more antennas and radio frequency channels are used in largescale phased array systems.The use of low-precision ADCs can effectively reduce system costs,but it will introduce quantization errors.Therefore,a neural network for reconstructing quantized signals is proposed.The network effectively improves the dynamic range of the Beidou anti-jamming system.Not only that,but the Direction of Arrival(DOA)estimation used to test the denoising effect of the network can be used to locate the interference source.The network adopts a fully connected design,and cooperates with residual blocks,batch normalization units,and Re LU activation functions to reconstruct high-precision signals from quantization noise.The simulation results show that this network can improve the signal accuracy of 1 bit,that is,improve the dynamic range of 6d B.Finally,the quantitative denoising network was verified in FPGA.5)Finally,the Beidou anti-jamming algorithm is implemented based on the FPGA platform,the hardware implementation steps of the algorithm are introduced in detail,and the actual measurement scenarios and processes of the system are described in detail.Finally,the actual measurement results and analysis of the system are given.It shows that the anti-jamming algorithm has 90 d B and 80 d B anti-jamming capabilities under a single broadband and three broadband interferences,respectively.