| Millimeter-wave radar is a key component of advanced driver assistance systems.With the development of the automotive industry,there are more and more millimeter-wave radars on the road.Among the many radar systems,the linear frequency modulation continuous wave radar system is widely used in the automotive field due to its low cost,small size and high measurement accuracy.With the increase in the number of millimeter wave radars and limited spectrum resources,the problem of mutual interference between radars will become more prominent.The interference between chirp continuous wave radars can be divided into cross interference and parallel interference.Cross interference will increase the noise floor in the frequency domain and reduce the detection performance of the radar;parallel interference will generate ghost targets,causing the radar to produce false alarms.The above two kinds of interference will affect the normal operation of the radar,but the probability of parallel interference is low,so the main research object of this article is cross interference.Aiming at the mutual interference between FM continuous wave radar systems,antijamming technologies such as time domain,frequency domain,polarization domain,space domain,and waveform coding have been used.For cross interference,this article carries out interference suppression from the perspective of time domain.The main research contents of this paper are as follows:(1)The principle and influence of mutual interference between linear frequency continuous wave radars are analyzed,and the radar echo model containing interference signals is deduced.The theoretical derivation proves that cross interference will increase the noise floor in the frequency domain,and the typical interference scenarios show that the power of the interference signal is much higher than the power of the echo signal,indicating that interference is a factor that cannot be ignored for radar detection.(2)Based on the difference between the echo signal and the interference signal,the traditional fixed threshold detection method is improved.The improved method can still achieve a good interference detection effect even in the case of multiple interference sources.On the basis of interference detection,an autoregressive model is proposed to reconstruct the sampling points of the interference area.Experimental results show that this method not only solves the effect of high sidelobes caused by the zeroing method,but also has a good interference suppression effect.(3)The method of detecting and suppressing interference can achieve the purpose of interference suppression,but it ignores the fact that signals in the interference area also contain useful signals.Aiming at this problem,an interference suppression method combining empirical mode decomposition and autoregressive model is proposed.The first is to perform empirical mode decomposition on the echo containing interference signals to obtain a series of intrinsic mode functions.Then according to the energy of the autocorrelation function of each mode,the modes dominated by the interference signal and the useful signal are determined respectively.Finally,while retaining the mode dominated by the useful signal,further processing is performed on interference-dominated intrinsic mode functions and the processed modes are added to the mode dominated by the useful signal to obtain the final signal. |
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