Research On DOA Estimation Method Of Nonuniform Ultrasonic Array

Ultrasonic level detection methods play an important role in many fields such as meteorology,hydrology and ocean,and it is of great significance to improve the accuracy of level detection.For the problem of limited ultrasonic array structure and complex reflected echo in a narrow space,the joint estimation method of the Direction of Arrival（DOA）for Multiple Input Multiple Output（MIMO）ultrasonic detection system is studied,and the research of non-uniform ultrasonic array detection is carried out on this basis.This paper firstly studies the structure of MIMO ultrasonic array in depth,mainly analyzes the relationship between the array arrangement and the number of virtual array elements,and forms a non-uniform MIMO ultrasonic array structure with non-overlapping virtual array elements based on the phase center approximation principle.Then,in a narrow space,the reflection of ultrasonic waves forms multipath propagation,and there will be complex correlated signal interference,resulting in a high degree of correlation between adjacent transmitted signals and a high degree of cross-correlation between different transmitted signals.To solve the problem of low spatial resolution due to correlation,the method of vector singular value is used to reconstruct the matrix of the eigenvector corresponding to the maximum eigenvalue of the source,which improves the estimation accuracy of the coherent signal.Finally,for the accurate estimation of ultrasonic echo signals,a DOA and time delay estimation method based on MUSIC algorithm is adopted.This method uses two one-dimensional spatial domain S-MUSIC and one one-dimensional T-MUSIC algorithm combined with Temporal filtering and spatial filtering techniques.Compared with the traditional algorithm,this method can estimate the DOA and time delay of the signal with high resolution,and has good anti-noise performance.The application of the DOA and time delay joint estimation method in liquid level measurement is verified by simulation experiments.The results show that this method has improved measurement accuracy compared with the ultrasonic phased array method in the detection of dynamic liquid level.At the same time,the factors affecting the measurement accuracy are also analyzed experimentally,which further shows the measurement performance of the method in this paper under different conditions.