Research On Distributed Coherent Synthesis Technology On Motion Platform

With the development of information technology,the electromagnetic environment in the battlefield has become more and more complex,which is facing more and more challenges for radar seekers.If multiple radar seekers work together,it can not only improve the range of the radar,but also solve the shortcomings of a single seeker that is difficult to find a low observable target.Based on this background,this paper applies the basic principle of ground distributed radar to the air motion platform to construct the air distributed coherent system.Compared with the ground distributed system,the realization of the air distributed coherent system is more difficult.Because the target and seeker are moving,and the baseline will not be fixed.Therefore,this paper focuses on the problem of coherent parameter estimation and signal processing flow under the mobile platform.The specific work of this paper is summarized as follows:1.A distributed coherent system is established on motion platform,which can work in three modes of MISO,MIMO and full coherent.Corresponding signal models are constructed for each mode.The signal model is constructed with full consideration of the impact of the speed of the platform and the speed of the target on the echo.2.It is verified that the distributed coherent system on motion platform can be synthesized coherently under the mode of MISO,MIMO and full coherence.The magnitude of the compensation amount of the coherent parameters when the system works in the transmit coherent mode of the full-coherent mode is calculated.The effects of time-delay and phase coherence parameters on the performance of coherent synthesis are analyzed.The phase and delay estimation accuracy requirements for the signal-to-noise ratio(SNR)gain reduction of less than 1 dB are given for the MISO and MIMO modes.For the full coherent mode,the effects of phase and delay estimation accuracy on the coherent synthesis are simulated separately when transmitting coherent and receiving coherent.The phase and delay estimation accuracy requirements for the SNR gain reduction of less than 3dB are given.Range sum(R_s)is the key factor affecting the estimation of coherent parameters,so the influence of range sum on the performance of coherent synthesis is discussed.The relationship between range sum root mean square error and launch angle,baseline length and other factors is simulated.In addition,the influence of the target speed estimation deviation and the speed error provided by the platform inertia on the coherent of the full-coherent mode transmission is analyzed.The speed estimation accuracy requirement when the gain loss does not exceed 3dB is also given.3.For the coherent parameter estimation problem,four methods of peak extraction method,cross correlation processing method,MUSIC ranging method and phase ranging method are simulated.Among them,the peak extraction method and the cross-correlation processing method are used for time delay and phase coherent parameter estimation,and the MUSIC delay estimation method and phase ranging method are used for delay parameter estimation.And each method has been verified by simulation.Finally,four parameter estimation methods are compared from the input SNR and signal bandwidth.It is concluded that the phase ranging method is better than the four methods to better meet the estimation accuracy of the delay parameters of the distributed coherent system when operating in the full coherent mode.For the phase coherent parameters,the peak extraction method or the cross-correlation processing method can satisfy the requirement that the coherent synthesis gain loss does not exceed 1 dB.