Research On Interference Suppression Algorithm Of Automotive Millimeter Wave Radar

With the increasing popularity of automotive millimeter-wave(MMW)radars,the number of vehicles equipped with MMW radars continues to increase.When multiple MMW radars operate in the whole or part of the frequency band at the same time,the radar systems will cause mutual interference.According to the modulation slope of the radar signal and the interference signal,the interference type can be divided into wide-band interference and narrow-band interference.Because the probability of narrow-band interference is extremely low,this thesis mainly studies wide-band interference.The interference signal appears as an impulse-like signal in the time domain and a white noise signal in the frequency domain.The mutual interference between automotive MMW radars increases the noise floor,even submerges the information of targets and creates ghost targets.In order to solve this problem,this thesis studies the interference suppression algorithms for single receiving antenna radars and multiple receiving antennas radars,respectively.The main research content of this thesis is as follows:(1)An interference suppression method for automotive MMW radars based on empirical mode decomposition is proposed,which is used to measure target distance of single receiving antenna radars in the case of mutual interference.Firstly,the empirical mode decomposition is used to process the received signal and obtain a series of components,and then continuous mean square error method is used to determine the components that contained interference signal.Finally,the threshold method is used to suppress the interference signal in the components.Because the traditional threshold method will cause signal discontinuity and loss of useful signal,the proposed method improves the threshold method for suppressing interference signal.The proposed method can mitigate the interference effectively while keeping the signal continuous and reducing the loss of useful signal.To further suppress interference signal,the thesis used the proposed method iteratively.The improvement of the SNR of targets will converge to a constant value when the number of iterations reaches a certain value.The results of simulation and field experiments show that the proposed method can obtain accurate target distance in the case of mutual interference between automotive MMW radars.(2)An interference suppression method for automotive MMW MIMO radars is proposed,which is used to measure target angle of multiple receiving antennas radars in the case of mutual interference.Because the mutual interference between automotive MMW radars will reduce the SNR of the reflected signal from target,it is difficult to accurately distinguish the signal subspace and the noise subspace of the received signals,which will degrade the accuracy of the traditional DOA estimation algorithm.For the automotive MMW MIMO radars with multiple receiving antennas,the proposed method first detects the signals of receiving antennas affected by the interference signal in the received signal matrix,then the signal affected by the interference is decomposed through empirical mode decomposition,and then suppresses the interference signal components.Finally,all the received signals are synthesized into a new received signal matrix and input to the DOA estimation method.The results of the simulation and field experiments show that the proposed method can obtain accurate DOA estimation in the case of mutual interference between automotive MMW MIMO radars.