Direction‐of‐arrival estimation for far‐field acoustic signal in presence of near‐field interferences

Abstract

The far-field acoustic signal received by an acoustic array is frequently affected by near-field interferences. This causes deterioration of the direction-of-arrival (DOA) estimate for the far-field signal. To enhance the DOA estimate, the novel near-field/far-field (NFFF) beamformer is proposed. Such a beamformer optimises the beam pattern for far-field detection by maximising the beamformer output in the direction of the far-field target signal with the imposed condition to eliminate interfering signals from near-field locations. As the interference suppression only occurs at specific positions of near-field interferences, a blind zone in the far-field direction present in conventional methods will not be introduced. The NFFF beamformer is also applicable for coherent signals and for multi-interferers. For a stationary situation where interferers' locations are fixed, the NFFF beamformer computations do not require time updates and the computational load is similar to that of the conventional beamformer. The method can be extended to several situations such as acoustic monitoring performed from a stationary platform subjected to water currents, waves, winds and other variables, all of them generating nearby interferences, and also to different array configurations including two-dimensional (2D) and 3D arrays.

A Sparse Perspective for Direction-of-Arrival Estimation Under Strong Near-Field Interference Environment

“…The noise power can be obtained by plugging the results of Equation (26) into Equation (25). If the number of sources is already known, the noise power can be estimated directly from Equation (25).…”

“…However, a blind region persists in the far-field as near-field interference is suppressed. Other spatial filters have also been proposed for interference suppression [24][25][26] while cannot achieve satisfactory performance when the signal of interest and the interference have a similar orientation.…”

Direction-of-Arrival Estimation of Far-Field Sources Under Near-Field Interferences in Passive Sonar Array

“…In addition, the phase mismatches by the DAS cause a masking region with a large and wide beam in the azimuth domain [5,6]. When the DOA of the far-field source lies in the masking region, the DOA estimation of the far-field sources becomes difficult to achieve with near-field interferers [7][8][9][10][11].…”

“…Interference mitigation techniques in sonar arrays have been researched to solve masking problems [11,12]. In [11], a near-field/far-field (NFFF) beamformer, which is based on a minimum variance distortionless response (MVDR), was studied to remove near-field interference by the weight vector of the beamformer. The NFFF beamformer, however, required the same center frequencies of the far-field sources, which is impractical.…”

DOA estimation for mixed signals with gain-phase

“…Leong [28] proposed a technique for active detection and estimation of the range, radial velocity and DOA of multiple moving closely spaced targets in the three-dimensional space for both farfield and near-field cases. Zhang [29] optimized a beamformer pattern for far-field detection by maximizing the beam-former output in the direction of the far-field targets with the imposed condition to eliminate interfering signals from near-field locations. Based on the polynomial decomposing method and high-order cumulant technique, Wang [30] estimated DOA of these signals without any spectral search and parameter matching procedure.…”