Near-field Beamforming Algorithm And Its Application Research

Array signal processing system is popularly applied in sonar, spaceflight, radar and so on. And it basically covers two key technologies:source parameter estimation and beamforming. The existing array processing system mostly is based on the assumption of the far-field conditions, but the plane wave model is applicable only when the target is in the far field of the array. The far-field hypothesis model is not appropriate when the target is in the near field. If the far-field assumption is still adopted when processing the near-field array signal, it will bring the processing result down even failure. This paper mainly studies the near-field array signal processing algorithms based on the sphere wave model, and the several aspects of content are as follows:(1) The near-field array signal processing model is studied;first of all, this paper deduces the near-field array response matrix based on the array sphere wave model, and makes a comparison between the far-field array response matrix and the near-field one. Second, it adopts the LMS algorithm for an example in the near-field adaptive beamforming algorithm simulation, and realizes the separation of two signals at the same direction but different distances.(2) The near-field narrowband beamforming problem is studied; for the narrowband beamforming, this paper’s study mainly includes the near-field conventional beamforming algorithm (delay and sum beamforming) and constraint optimization beamforming algorithm. For phased array beamforming system has the defect of complicated control and high cost, this paper puts forward a simple near-field beamforming algorithm based on the weighted amplitude theory; under the narrowband condition, this paper also investigates the near-field space energy distribution problem, and deduces the power density distribution at any point of the near-field range for an array.(3) The near-field broadband constant beam width beamforming problem is studied; this paper mainly studies the near-field constant beamwidth beamforming algorithm including the far-near field conversion and virtual transformation broadband constant beamwidth beamforming algorithm, and proposes a window function method to design the near-field2-D constant beamwidth beam.(4) Finally, this paper studies the broadband source localization method. First, it analyzes the advantages and disadvantages of the existing common near-field source localization methods, and then proposes a new near-field broadband source localization algorithm based on the theory of subspace included angle. The new algorithm can avoid the source location prediction and broadband focusing processing.In this article, the near-field beamforming and wideband source localization problems are analyzed and studied based on the sphere wave model.Through the calculation and simulation, some instructional conclusions and references are drawn for the near-field array signal processing.