Research On Distributed MIMO Radar Waveform Design Technology

MIMO radar is composed of multiple transmitters and receivers.MIMO radar has a great potential in improving the radar performance such as degrees of freedom,angular resolution,and parameter recognizability,and thus has received extensive attention in recent years.MIMO radar can usually be divided into two types: co-located and distributed.Among them,distributed MIMO radar can overcome RCS scintillation and obtain more target statistical information through spatial diversity.The premise of achieving this performance is that the target echoes from different transmitters can be effectively separated at the receiver.Therefore,it is usually required that the transmitted signals are mutually orthogonal.In this thesis,the orthogonal waveform design of distributed MIMO radar is explored.The main contents are summarized as follows:Based on the research and analysis of the basic principles of MIMO radar,distributed and co-located MIMO radar signal models are established,common orthogonal waveforms are analyzed and the optimization design criteria for orthogonal waveforms are summarized,and the signal processing model at the receiver of MIMO radar is introduced.An optimized design model for OFDM phase-coded waveforms is given.The idea of OFDM is introduced in the design of distributed MIMO radar signal.Each transmitted signal is composed of a set of orthogonal subcarriers to achieve frequency diversity,and each subcarrier is phase-encoded to ensure the orthogonality between different signals.In this thesis,the mathematical model of OFDM phase coding is given first,and the MTI processing performance improvement brought by the signal frequency diversity is deduced.And then,the OFDM phase-coded signal set is constructed by using a genetic algorithm with weight-adaptive mechanism.The design methods of orthogonal LFM signal is studied.Firstly,the OFD-LFM signal set is constructed by frequency division and the influence of different frequency intervals on the orthogonality of OFD-LFM signal is analyzed.The application of OFD-LFM signal has certain limitations.Under the condition that there is a large number of transmitted signals,the excessive bandwidth of OFD-LFM signals will bring challenges to the practical engineering of the radar system.Therefore,an orthogonal multi-segment LFM signal optimization design model is presented in this thesis.In a given pulse width,the signal consists of three chirps.The orthogonal signal is constructed by adjusting the frequency slope of the three chirps.A genetic algorithm is used to obtain a set of orthogonal multi-segment LFM signals.Finally,aiming at the shortcoming of the high sidelobe of LFM signal,a mismatched filter optimization design model under the condition that the SNR is controllable is given,and its effectiveness is verified through simulation.The problem of OFD-NLFM signal design is studied.Firstly,the principle of NLFM signal design by using the window function method is analyzed,and the NLFM signal performance obtained by using different window functions is compared.Then,the NLFM signal is designed based on the form of the combined window function.Finally,the OFD-NLFM signal model is constructed.The orthogonal signal set is obtained through simulation and the influence of frequency interval on the orthogonality of OFD-NLFM signal is analyzed.