A near-field time-domain beamforming method for wideband signals

Abstract

The invention discloses a near-field time-domain beamforming method suitable for broadband signals. According to the index requirements of the expected beam pattern and under the far-field assumption conditions, the far-field beam weight is designed by using the existing far-field beamforming technology. coefficient and determine its time-domain implementation structure; according to the distance r from the near-field signal source to the center of the matrix, modify the far-field beam weight coefficient to obtain the near-field beam weight wm; determine the correction weight coefficient required in the near-field beamforming Accurate time delay; using windowed least square error method to design finite impulse response fractional time delay filter banks to achieve the precise time delay required in near-field beamforming; the fractional time delay filter designed in step (d) The group is added to the time-domain beamformer determined in step (a), that is, the realization structure of the near-field time-domain beamformer is obtained. The invention is simple and effective, is suitable for real-time coefficient updating, and is suitable for broadband signals, and the design complexity and feasibility are greatly improved.

Description

technical field The present invention relates to the beamforming technology in the field of array signal processing, in particular to the beamforming technology under near-field conditions and its time-domain implementation method. Background technique Beamforming is an important technique widely used in radar, sonar, ultrasound imaging and wireless communication. The present invention considers the beamforming process at the receiving end. In practical systems, multiple sensor array elements are often used to form a basic array according to certain geometric rules. The so-called beamforming is to process the output of each element of the basic array through certain processing, so that the total output of the array reaches the maximum in a certain direction, and the other directions become smaller accordingly. A beamformer can be regarded as a spatial filter, which can filter out signals at certain orientations in space and only allow signals at specified orientations to p...

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Problems solved by technology

But if the time delay in the near-field compensation term cannot be realized with high accuracy, then the performance of the near-field beamformer will be greatly affected

Nearfield Broadband Array Design Using a Radially Invariant Modal Expansion. J Acoust Soc Amer, 2000, 107(1): 392~403), but this method is very complicated to design because it involves the harmonic solution of the wave equation