Research On Superdirectivity Algorithm Of Cylindrical Array

In the conventional array signal processing,when the array element spacing is equal to half wavelength,if the signal frequency is relatively low,in order to get the certain spatial gain,the array size must be very large,distributed implementation difficulties.In the space of homogeneous isotropic noise field,super-directional algorithm in the small wavelength dimension,according to the correlation of receiving noise signal between each element,through the optimization weighted sum to obtain the best processing gain.Compared with the conventional array processing,the algorithm has a great advantage in low frequency signal range.Theoretically,any one of the small size of the array,when the element spacing and wavelength is relatively small,through the super-directional optimization process,we can get a higher space processing gain and narrower main lobe width,with a high spatial resolution;And the main lobe width changes little with the signal frequency.In this paper,we study the characteristics of the super-directivity algorithm in the low signal frequency range.The simulation and experiments show that the algorithm has the advantages of narrower main lobe width,higher array gain and spatial resolution.The algorithm has a good application prospect for the detection,estimation and resolution of low frequency signals by using the small scale array.The main research work of this paper can be summarized as follows:introduces the research background and current situation of the super-directional algorithm,and starts from the basic theory of the algorithm,and discusses the characteristics of the algorithm in detail;According to the algorithm theory model,carried out a variety computer simulation for different array patterns,Including the linear array,the circular array,the planar array and then the stereoscopic array,and the performance of the algorithm from various aspects,such as the main lobe width,array gain,spatial directivity and so on,made a detailed discussion and analysis.In this paper,the performance of the super-directional algorithm is compared with that of the conventional beamforming algorithm,got the performance benefits of the super-directional algorithm and its frequency applicable scope.A matrix correction technique,namely diagonal loading,is introduced and partially simulated.It shows that the covariance matrix can be modified by this technique,thus improving the performance of super-directional algorithm.In order to verify the performance of the super-directional algorithm,we carried out the corresponding pool experiment and lake experiments,based on double cylindrical array,single frequency signal and multi-line spectrum signal,the noise measurement performances of the two algorithms are tested and compared,and the performance advantage of the super-directional algorithm was fully demonstrated.Simulation and experimental results show that the super-directivity algorithm has a great advantage in detecting and resolving low-frequency signals compared with conventional beamforming algorithms,the algorithm can use smaller-sized arrays in the low frequency band to obtain narrower main lobe width,higher system process gain and lower side-lobe,which means that the use of super-directional algorithm can greatly improve the low-frequency noise measurement performance.