MIMO Waveform Optimization Design Based On Frequency Control

Multiple Input Multiple Output(MIMO)radar is a new system radar.MIMO radar has significant advantages in clutter suppression,target detection,parameter estimation,and transmitting power pattern synthesis based on waveform diversity.The optimal design of radar waveform is the most basic and important research content in radar system.Waveform diversity in MIMO radar provides more degrees of freedom for waveform optimization design,which makes MIMO radar waveform optimization design more flexible.This paper mainly optimizes the specific structural waveforms in MIMO radar,including multi-carrier waveform and phase-code waveform,and achieves specific optimization by frequency control.For multi-carrier waveforms,a generalized and universal Frequency Division Linear Frequency Modulation-Phase Code(FD-LFM-PC)waveform is mainly studied.In order to achieve the optimization purpose such as reducing the time domain sidelobe,optimizing the ambiguity function,matching the spatial transmitting power pattern,the carrier frequency order and carrier frequency interval is optimized.For phase-code waveforms,we mainly study a spectrum-limited sequence set with unimodular multiphase sequences,including complementary sequence sets and orthogonal sequence sets.So,this paper achieves the sequence set with optimized power spectrum density and related performance.The main work of the paper is as follows:In the first part,the space-time optimization for the Orthogonal-FD-LFM-PC(OFD-LFM-PC)waveform by controlling carrier frequency coded.OFD-LFM-PC waveform is a multi-carrier waveform with carrier frequency orthogonal.Firstly,this paper analyses the space-time performance of OFD-LFM-PC waveform,and the analysis showed that it can suppress the autocorrelation grating lobe of the OFD-LFM waveform.At the same time,it has lower autocorrelation sidelobe compared to the OFD-LFM waveform.Secondly,the OFD-LFM-PC waveform optimization model based on carrier frequency control is established.The waveform optimization parameters are carrier frequency coded and phase-code matrix modulated on carrier,and the purpose is peak sidelobe level of autocorrelation function and omnidirectional transmitting power pattern.The optimization model shows that the model is a multi-objective multi-variable nonlinear discrete optimization model.Finally,a particle swarm algorithm nested genetic algorithm is proposed to optimize the phase-code matrix and the carrier frequency coded.The simulation results show that the proposed algorithm can effectively solve the above optimization model,and the optimized waveform can effectively reduce the autocorrelation sidelobe level while maintaining the transmitting power pattern omnidirectional,thus the optimization waveform enhance the radar detection performance.In the second part,the space-time optimization for the FD-LFM-PC waveform by controlling carrier frequency interval.FD-LFM-PC waveform is a multi-carrier waveform whose carrier frequency is not orthogonal.Firstly,the time domain ambiguity function characteristics and spatial domain transmitting power pattern characteristics of FD-LFM-PC waveforms are analyzed,and the time domain characteristics of FD-LFM-PC waveforms are compared with FD-LFM and FD-PC waveforms.The analysis shows that the FD-LFM-PC waveform proposed in this paper can eliminate the ambiguity grating sidelobe and the Distance-Doppler coupling of the FD-LFM waveform.At the same time,the waveform proposed in this paper has more waveform parameters,so it has more optimization space.Secondly,the FD-LFM-PC waveform optimization model based on carrier frequency interval control is established.The optimization parameters are carrier frequency interval,LFM-PC waveform bandwidth modulated on carrier,phase-code matrix,and the purpose is reducing the sidelobe of ambiguity function and matching the different transmitting power pattern.The optimization model is a two-objective constrained optimization model,which includes linear constrained optimization and nonlinear constrained optimization.Therefore,a step-by-step constraint optimization method is proposed.Finally,we choose the sequence quadratic programming and adaptive clone selection algorithm to solve the above model.The simulation results show that the proposed algorithm can effectively solve the above optimization model,and the optimized waveform has better correlation performance,and can match the requirements of different transmitting power pattern.In the third part,phase-code sequence set design with power spectral density control.Both complementary sequence set and orthogonal sequence set have good correlation performance.Firstly,the existing complementary sequence set and orthogonal sequence set are analyzed in this paper,the analysis shows that the sequence length,number and phase number are limited,and the spectrum energy random distribution.Secondly,taking the phase of the phase-code sequence set as the optimization variable,the optimization model mixed the weighted integral sidelobe level and the weighted power spectral density is established,and it is a linear unconstrained optimization model.So,a Complementary Sparse Frequency Waveform set(CSFWS)and an Orthogonal Sparse Frequency Waveform set(OSFWS)are designed.Finally,a fast algorithm based on conjugate gradient descent is proposed to solve the above optimization model.The simulation results show that the algorithm based on conjugate gradient descent can solve the above two sequence set problems,and the algorithm in this paper has higher computational efficiency than other known algorithms.