Research On Waveform Optimization Technology Of Intra-pulse/Inter-pulse Frequency Agile Cooperative Detection

Modern radar is faced with the increasingly complex situation of electronic countermeasures,so the anti-jamming ability becomes a key index to measure the radar performance.Frequency agility has been widely used for modern radars.Interpulse agile frequency conversion and intrapulse agile frequency conversion are two common frequency agile methods of frequency agile radar.At the same time,the anti-jamming ability of radar system is closely related to the complexity and randomness of radar signal.Therefore,it is a better choice to use compound modulated signal which can greatly increase the difficulty of detection,recognition and tracking by enemy jammers.In addition,when modern radar is faced with the challenge of multi-target and group targets,a single radar is not enough and instead use cooperation detection.The coherent performance gain can be obtained through radar cooperative detection.At the same time,the detection performance can be improved by fusion processing of data from multiple radars.This dissertation systematically studies the theory and method of the intrapulse/interpulse agile frequency agility cooperative detection waveform optimization technology.The main work carried out includes:1.Aiming at the problems of high sidelobe level and weak anti-interference ability of traditional FSK-PSK composite modulation signal,this dissertation proposes an intrapulse frequency conversion FSK-PSK radar waveform optimization method.On the basis of the detailed derivation of signal ambiguity function,two optimization models are established:1)The optimization model was established with the minimum integral sidelobe as the criterion and the discrete phase coding sequence as the optimization variable;2)The optimization model was established by minimizing the weighting sum of the sidelobe level of the autocorrelation function and the sidelobe level of the cross-correlation function of the subpulse signal,fixing the frequency hopping coding sequence,and the discrete phase coding sequence was used as the optimization variable.Two optimization models were solved based on ADMM and ADMM-MM algorithms.The results show that compared with the GA algorithm,the first optimization model can reduce the sidelobe level better,and the convergence speed is faster,which is more suitable for engineering use.The second optimization model can realize the combined suppression of autocorrelation sidelobe and cross-correlation sidelobe,which can be used to counter the repeater jamming.2.Aiming at the problem that in the cooperative detection and receiving mode of radar,waveform orthogonality among channels is not good,resulting in interference between waveforms,this dissertation proposes an optimization method of cooperative detection waveform based on FSK-PSK interpulse orthogonal coding,and solves the optimization method based on ADMM and ADMM-CD algorithms.The results show that compared with the traditional PSK signal and GA algorithm,the proposed method can reduce the sidelobe better.The simulation results of multi-radar cooperative detection show that the proposed optimization method can reduce the sidelobe better than non-coherent method under the condition that the phase modulation coefficient and code length are the same.3.Aiming at the problem of high sidelobes of frequence-phase coding joint agility signal after pulse compression processing,this dissertation proposes a waveform optimization method of cooperative detection with FA-PSK radar signal.On the basis of the detailed derivation of the signal ambiguity function,the optimization model was established by minimizing the integral sidelobe in the center strip of the ambiguity function as the optimization criterion,and the optimization method was solved by three algorithms:ADMM,ADMM-MM and Multi-CAN.The results show that compared with the GA algorithm,the proposed optimization method can better reduce the sidelobe,and improve the detection ability of the radar signal after pulse compression.The simulation results of multi-radar cooperative detection show that the two optimization algorithms based on ADMM-MM and Multi-CAN can reduce the sidelobe better than non-coherent method under the condition that the phase modulation coefficient and code length are the same.4.Aiming at the problem that the phase error compensation of each sensor on each frequency is required for cooperative detection,the phase error compensation and sparse scene reconstruction methods under the interpulse agility frequency conversion cooperative detection are proposed.On the basis of the detailed derivation of the phase error model under the cooperative detection,the minimum norm optimization model is established based on the two-dimensional sparsity of the target distance and velocity,and the optimization algorithm is constructed by the alternate direction multiplier method.The results show that the proposed method can make the restored target scene have the characteristics of two-dimensional(range-velocity)low sidelobe.The proposed sparse constraint optimization algorithm based on ADMM has faster computing speed and iteration efficiency.