Research On Interference Suppression Technology Of FMCW Radar Based On Adaptive Beamforming Algorithm

In recent years,with the continuous improvement of people’s quality of life,the number of vehicles equipped with FMCW radar has continued to increase,the possibility of multiple radars overlapping in time and space has increased,and the possibility of mutual interference between radars has also increased.,which may cause the radar system to be unable to accurately obtain the target’s position and speed information or even to detect the target,resulting in serious traffic accidents,resulting in personal safety and personal property losses.Therefore,suppressing the mutual interference between FMCW radars is of great significance to ensure the safe driving of vehicles.As one of the important technologies to suppress the mutual interference between radars,adaptive beamforming technology has been a research hotspot of scholars since its application.Adaptive beamforming technology is a spatial filtering technology,which uses the sampling data of the array antenna to obtain the weighted vector through the corresponding algorithm,so that the main beam of the antenna is aligned with the desired signal direction,and the null point is aligned with the direction of the interference signal,so as to suppress the interference signal.However,in the actual application process,due to human factors or technical limitations,the ideal situation is difficult to achieve,and there will inevitably be various errors,which lead to the interference suppression effect of the traditional Capon beamforming algorithm is not as expected.And at present,there are relatively few simulation studies that apply the robust beamforming algorithm to the actual driving of simulated vehicles.Therefore,in order to improve the robustness of the beamforming algorithm and verify the simulation effect of the algorithm in the process of vehicle driving,this paper studies the FMCW radar interference suppression technology based on the adaptive beamforming algorithm.The main research contents of this paper are as follows:(1)Aiming at the problem that the expected signal steering vector mismatch caused by the estimation error of the incident direction or the local coherent scattering reduces the signal-to-interference-noise ratio of the system output,this paper proposes a variable loading value based on the diagonal loading technology to improve robust adaptation.Beamforming algorithm.The algorithm first decomposes the eigenvalues of the sampled covariance matrix,and uses the ratio of the maximum and minimum eigenvalues to estimate the input signalto-noise ratio;then uses the forward and backward spatial smoothing technology to process the covariance matrix,and then uses the ratio obtained before.For diagonal loading,different diagonal loading factors are adaptively selected according to different situations;finally,the desired signal steering vector is optimized according to the theory of characteristic subspace.Without sacrificing a large amount of computational complexity,the method enables the beamforming system to still have a good suppression effect on the interference signal and a high output signal interference-to-noise ratio when there is a steering vector mismatch error,(2)Aiming at the problem that the target cannot be accurately identified when there are coherent and incoherent interference signals with the working FMCW radar in the space at the same time,this paper proposes a robust method based on particle swarm algorithm waveform optimization and signal plus interference covariance matrix reconstruction.Adaptive beamforming algorithm.In this method,before the radar signal is transmitted,the particle swarm algorithm is used at the system transmitter to optimize the waveform according to the interference signal parameters in the current environment obtained by the receiver,so that the correlation between the interference signal and the working radar signal is minimized.After that,by reconstructing the signal plus interference covariance matrix and optimizing and correcting the steering vector of the desired signal,the effect of suppressing the interference signal when the steering vector of the desired signal is mismatched is realized.Finally,the scene of the car driving on the road is simulated.At this time,there are both coherent and incoherent interference signals in the space with the working radar signal.Using the method proposed in this paper can accurately identify the real targets’ speed and distance information.And as well it has a good interference suppression effect through simulation.