Performance of sinusoidally deformed hydrophone line arrays

Abstract

It is well known that array deformations can distort beam patterns and introduce bearing errors if the beamformer assumes linearity. It is also known that deformed arrays can resolve left-right ambiguities, provided the shape is known. In this work, these two effects are studied for undamped and damped sinusoidally deformed arrays with small deformation amplitudes in the horizontal (x,y) plane only. By use of fixed arc-length separations along the array, the hydrophone (x,y) coordinates are determined numerically and the error in assuming equal x spacing is summarized for a sample array. Array-response patterns are analyzed for two conditions: ͑1͒ when the deformed array shape is assumed linear and ͑2͒ when the deformed array shape is known exactly. Degradations resulting from assuming linearity and the ability to resolve left-right ambiguities are discussed in terms of reduced gain, degraded angular resolution, and bearing errors. Shape-unknown signal-gain degradation ranges to 7 dB at broadside, but is less than 1 dB near endfire. For the shape-known case, signal gain for the true peak is greater than signal gain for the ambiguous peak by up to 9 dB for sources at broadside and to just over 2.5 dB for arrivals near endfire.

Adaptive beamforming of a towed array during a turn

“…9. This is similar to the wider 3-dB beamwidth that can be observed for the mirror track [4]. The latter feature can be seen in Fig.…”

“…For the curved array, the steering vectors are computed based on the phase delay for each of the hydrophones (5) where is the reference sound speed and is the component perpendicular to the wavefront as determined by (4). The range to the source is not modeled.…”

“…During maneuvering, a horizontal line array will not be straight and this will cause performance degradation for beamforming acoustic signals [3], [4]. This degradation will be more severe for adaptive beamformers which are more sensitive to errors in hydrophone location.…”

Standard target calibration: Practical inter-comparison with planar surface targets and calibrated transducers

“…Analytic derivations exist for the acoustic scattering from corrugated surfaces [9] and for the degradation in array gain in towed arrays [10,11]. In this case, a numerical estimation of the equivalent target strength reduction was performed and was in good agreement with the variance obtained from the acoustic measurements of the surface.…”

Left right discrimination performance improvement for the line array sonar system

“…[2][3][4][5][6] 그 중에 하나인 카디오이드(cardioid) 빔형성 기법은 매우 근접한 센서 쌍을 이용하여 카디오이드 빔형성을 통해 좌 우를 구분한다. 신호원으로부터 발생되어 배열의 입력이 되는 신 호를 라 하고 다음 식으로 표현된다.…”