Interference cancellation for uniform line arrays
John H. Stockhausen, Joseph B. Farrell · The Journal of the Acoustical Society of America · 1985
The effect of strong directional interference in an acoustic field is to mask small signals at nearby bearings. This paper presents a technique for reducing the effect of such interference on the performance of a uniform line array. A smoothed estimate of the interference bearing is obtained and a reference beam is steered in that direction. A single point inverse Fourier transformation of the reference beam signal results in a set of element excitations which are used to characterize the interference. These excitations are subtracted from the original excitation data, nulling the interference in subsequent beamforming. The null has an effective angular width (related to beamwidth and noise directionality), and the structure of the field map near the interference direction is obscured by the steep slopes of the null. Normalization of the map with respect to the ideal null shape restores much of the hidden structure and at the same time substantially reduces the bias of signal direction estimates.