| With the advent of the era of intelligent driving,millimeter-wave radar has become an indispensable sensor in the intelligent driving system because of its long detection distance,small size,low cost,not affected by the change of light intensity,strong ability to penetrate rain,haze,smoke and dust,which can work all day and all weather.In this context,major manufacturers and research institutions have invested in the wave of research and development of automotive millimeter-wave radars in an attempt to seize the market.Therefore,it is of great significance to study high-performance and low-cost automotive millimeter-wave radars and its key technologies.The main contents of this paper are summarized as follows:In this paper,the research status of automotive millimeter-wave radars and its key technologies is investigated.The working system and system composition of automotive millimeter-wave radars are introduced.The principles of ranging,velocity and angle measurement of FMCW radar are derived in detail.The principle of forming virtual aperture of MIMO radar is derived and the orthogonal waveform of MIMO radar is introduced in combination with automotive millimeter-wave radars.The moving target phase compensation technology of time division MIMO radar and the velocity ambiguity technology of automotive millimeter-wave radar are studied.Aiming at the problem of the extra phase term caused by the moving target coupled to the receiving antenna of the TDM MIMO radar,the coupled phase term is first analyzed.Then the compensation method based on Doppler frequency phase is improved to solve the problem that it can not compensate all moving targets in the multi-target scene,and the compensation effect of low SNR target is improved to a certain extent.The requirements of the method for the accuracy of velocity estimation are analyzed.Then,the principle of motion compensation method based on overlapping elements is studied and simulated,and the compensation effect of this method under amplitude and phase errors is analyzed through simulation.In addition,in order to the problem of reducing angle resolution of redundant elements in overlapping elements,a motion compensation method based on the phase difference of elements is proposed,which does not need overlapping elements and does not need to accurately estimate the target speed.It can complete the phase compensation of the moving target,and also through the simulation analysis of the compensation effect of the method in the case of amplitude and phase error.Finally,it summarizes the preconditions and adaptation scenarios of the three methods.Aiming at the problem of velocity ambiguity of automotive millimeter-wave radar,the phenomenon of speed ambiguity is first introduced and the necessity of understanding the speed ambiguity is analyzed.Then the principle analysis and simulation verification of the most commonly used method for resolving the velocity ambiguity of the repetitive staggered solution is summarized and the problems existing in the method are summarized.Then an improved ambiguity velocity defuzzification algorithm is studied,and the effectiveness of the improved method is verified by simulation.Comparing the improved method with the traditional method,we find that the data refresh rate of the improved method is improved,the complexity of the algorithm is reduced,there is no target matching problem,and the robustness is improved.Combined with the actual needs of an intelligent driving system,this paper designs a vehicle millimeter-wave radar system scheme which integrates the long-range mode and the short-range mode,and the vehicle millimeter-wave radar has a certain pitch detection ability.Firstly,a system scheme using two AWR1243 chips in cascade is designed,and the system composition and the role of each module are given.Then according to the index requirements of vehicle millimeter-wave radar for safe driving,the array design and waveform parameter design of the system are completed.Combined with the system scheme,the signal processing flow is designed.Finally,simulations were conducted to verify the two modes of the designed system,and the simulation results proved the effectiveness of the designed system.The radar system designed in this paper has both long-range and short-range modes,and the long-range mode and short-range mode receive array multiplexing,transmit array separation,and the two modes work alternately in time.Compared with the combination scheme of single long-range radar and short-range radar,the scheme uses the same number of high-performance radar chips,long-range mode and short-range mode.The number of array is doubled,and the radar angular resolution is greatly improved.The experimental system of MIMO millimeter-wave radar is set up.The target detection experiments are carried out in the outdoor with pedestrian and vehicle as the target,and the measured data are processed and analyzed.Firstly,the experimental system of MIMO millimeter-wave radar is introduced.Then the waveform parameters configured in the experimental system are introduced in detail.Finally,the experimental processing and analysis in two groups of experimental scenes are carried out to verify the validity of the signal processing algorithms of ranging,speed measurement,angle measurement and CFAR detection,and the trajectory of passengers and moving vehicles is extracted. |
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