Research On MIMO Radar Waveform Design Algorithms In Complex Electromagnetic Environment

With the rapid development of electronics and information technology,the demand and use of electronic devices,such as radar,communication and navigation have greatly increased,and the dense overlap of various types of electromagnetic signals in space makes the electromagnetic environment become more complex than ever.For radar system,the complex electromagnetic environment means a large number and variety of interference,as well as serious overlapping of frequency bands with other systems,which greatly restricts its performance.With the proposal and development of multiple-input multiple-output(MIMO)radar,it has become a hot topic of current research to improve the performance of radar in complex electromagnetic environments through waveform design,which takes advantage of MIMO radar transmitter diversity.According to the types of interference presented in the electromagnetic environment of radar,this thesis firstly discusses three MIMO radar waveforms design methods,which achieve interference suppression in the spatial domain,time domain,and joint spatialfrequency domain,respectively.Then,in view of the electromagnetic interference and frequency band congestion caused by the communication system,two waveform design methods based on the idea of‘co-operation and co-existence’are discussed,i.e.,co-design of radar and communication systems and integrated radar and communication waveform design.The main contents and innovations of this thesis are summarized as follows.1.Considering that signal-dependent interference is presented in the electromagnetic environment of a multi-mission MIMO radar,a joint transceiver design method based on sequence optimization(SO)algorithm and semi-definite programming(SDP)is proposed to enable the radar to perform search and tracking missions simultaneously.The method maximizes the transmit energy allocated in the search region and ensures that the received signal to interference plus noise ratio(SINR)of each known target is not less than a preset threshold.As a result,the radar can improve the detection probability of potential targets in the search region,and can effectively suppress interference to ensure the tracking performance of known targets.2.Considering that signal-independent interference is presented in the electromagnetic environment of a MIMO radar,two MM-based methods are proposed to design MIMO radar waveforms with anti-interference ability.The method considers that the optimal interference suppression filter is used at the receiver,and accordingly,it maximizes the output SINR of the filter while also optimizing the correlation performance between the filter and the waveform.As a result,radar detection performance can be improved since the interference is suppressed and the mutual influence between signals from different diversity channels and different range bins is reduced.3.Considering that both signal-dependent interference and signal-independent interference are presented in the electromagnetic environment of a MIMO radar,two alternating direction multiplier(ADMM)-based methods are proposed to design spectrally compatible MIMO radar waveforms.The method minimizes the waveform energy distributed in the spatial-frequency bands where the interferences exist,thereby reducing the impact of two types of interference on radar operation.Besides,the integrated sidelobes level(ISL)of the waveform is also constrained to ensure good separation between different waveform channels and the pulse compression characteristics after matched filtering.4.Considering that the communication system causes electromagnetic interference to the radar system,a joint optimization method is proposed for MIMO radar and multi-user MIMO(MU-MIMO)communication systems,which is developed based on block successive lower bound maximization(BSLM)and ADMM algorithms.The method jointly designs the radar transmit waveform,the hybrid beamforming matrices of the communication base station,and the fully digital beamforming matrices of the users.The target detection performance of the radar system is optimized by maximizing the mutual information between the received echo and the target response matrix.And the quality of service of the communication system is guaranteed by imposing constraints on the receiving SINR of the communication users.5.Since the communication system occupies a large amount of frequency band resources,the operating frequency band of the radar is congested and the available spectrum resource is very tight.Here,the dual-function radar-communication(DFRC)system is considered to tackle this problem,and a radar-communication integrated waveform design method is proposed based on the block successive upper bound minimization(BSUM)algorithm.Specifically,the template matching error of the transmit beampattern is minimized to make it suitable for target detection.Besides,the multi-user interference of communication is minimized so that the designed waveform also has good downlink communication performance.