Signal Acquisition And Algorithm Research Of Mmwave Automotive Radar System

Automotive millimeter wave radar emerges under the frequent traffic accidents,which is used for active protection from the origin of the accident.In this paper,a 77GHz with FMCW microstrip antenna and a set of signal processing system are designed to estimate the range,velocity and angle parameters of the target.In the part of signal acquisition,based on the theory of microstrip antenna,a microstrip antenna with two transmitters and four receivers is designed.The array is composed of four elements with a series of four rectangular patch elements and each receiving channel is independent.The gain of the antenna which contains receiving and transmitting is 30.75dB where the cross polarization is 50dB and the width of the H plane is 70 degrees.In the part of signal processing,based on FFT algorithm,a two-dimension FFT estimation method is proposed to estimate the velocity and range of the target.This method can accurately and efficiently estimate parameters of targets.The resolution for estimation increases with the number of fast and slow time sample points.Under the condition of 256 sampling points in fast time domain and 128 sampling points in slow time domain,the range resolution of target is 0.15m and the speed resolution is 0.38m/s.For the joint estimation of distance and angle,a space-time two-dimension MUSIC algorithm based on forward backward smoothing filter is designed which extends from the one-dimension MUSIC algorithm.This algorithm extends the one-dimension MUSIC algorithm to two-dimension domain.Because the original two-dimension MUSIC algorithm has a huge amount of computation,adding a smoothing window to reduce the size of matrix is designed.The algorithm can complete the distance and angle estimation,that is the position of the target can be determined.For the design of 4-element antenna in this paper,the algorithm can estimate the parameters of 3 targets.In the radar system,the part of signal capture is completed by the two transmit four receive microstrip antenna.The part of RF is completed by AWR1642,and the signal processing is implemented by FPGA.The application of two-dimension FFT algorithm and one-dimension MUSIC algorithm to FPGA needs some simplified operations.For the one-dimension MUSIC algorithm,the covariance matrix needs to be processed in parallel to reduce the operation time;the result needs to be processed in unitary transformation to facilitate the eigenvalue decomposition;for eigenvalue decomposition,Jacobi algorithm is used to iterate to complete the eigenvalue extraction;for tangent and trigonometric function calculation,CORDIC method can use addition and shift operation only;ROM is used to store data in exchange for computing resource.In the test,the system error is within the acceptable range,and the maximum detection distance is 100m.