| In the current research and development process of automotive assisted driving systems,millimeter wave radar has become a hot topic in the field of autonomous driving in recent years due to its advantages of all-weather and all-weather capabilities.However,in practical situations,existing onboard millimeter wave radars still have limitations in some road environments.In response to the target detection problem of vehicle mounted millimeter wave radar in high-speed environments,this thesis conducts optimization design research on the MIMO millimeter wave radar transceiver system,and designs and implements a MIMO radar system that can be used in high-speed environments;At the same time,research has been conducted on the optimization design of orthogonal waveforms to address the issue of cross correlation performance of multiple waveforms in orthogonal systems,in order to effectively improve the target detection performance of MIMO millimeter wave radar in high-speed environments.The work completed in this article mainly includes the following aspects:1.The orthogonal MIMO millimeter wave radar system was optimized and designed.In response to the problem of Doppler ambiguity in high-speed environments caused by Doppler ambiguity in traditional Time Division Multiplexing MIMO(TDM-MIMO)millimeter wave radar,a TDM-FDM-MIMO radar system based on Frequency Division Multiplexing MIMO(FDM-MIMO)and TDM-MIMO is proposed to improve the performance of traditional TDM-MIMO radar in velocity and angle measurement;At the same time,a phase modulation continuous wave MIMO(PMCW MIMO)millimeter wave radar system was proposed,which simplifies the angle measurement algorithm and further improves the maximum unambiguous speed.Finally,based on the proposed MIMO millimeter wave radar system,corresponding signal models were established and corresponding signal processing algorithms were designed for the target echo signal.2.Conducted the design and simulation of orthogonal waveforms.Aiming at the problem of poor orthogonality and anti-interference of traditional millimeter wave waveform,this thesis first introduces the design idea of orthogonal frequency division multiplexing on the basis of linear frequency modulated continuous wave,and designs and realizes the orthogonal frequency division linear frequency modulated continuous wave;Secondly,aiming at the problem that the existing phase coded signals have high sidelobe and short code bits and cannot obtain high processing gain,this thesis proposes an optimized genetic algorithm based on Walsh matrix constraint.By improving the generation method of initial population and fitness function in the genetic algorithm,the ultra long bit polyphase coded signals with better orthogonal performance and higher signal processing gain can be generated.3.Completed the simulation of high-speed target detection system for millimeter wave radar.In a high-speed environment,a linear array antenna layout with overlapping elements was designed to address the need for speed ambiguity resolution in traditional TDM-MIMO radar.At the same time,in order to achieve the functionality of 4D radar,a planar array antenna layout design was completed;Finally,a comprehensive simulation experiment was conducted combining the signal processing algorithm and orthogonal waveform of MIMO millimeter wave radar.Compared with the existing vehicle mounted millimeter wave radar system,the radar system proposed in this thesis has better performance in high-speed environments and simpler signal processing algorithms. |
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