Vector sensors and vector sensor line arrays: Comments on optimal array gain and detection

Abstract

This paper examines array gain and detection performance of single vector sensors and vector sensor line arrays, with focus on the impact of nonacoustic self noise and finite spatial coherence of the noise between the vector sensor components. Analytical results based on maximizing the directivity index show that the particle motion channels should always be included in the processing for optimal detection, regardless of self noise level, as long as the self noise levels are taken into account. The vector properties of acoustic intensity can be used to estimate the levels of nonacoustic noise in ocean measurements. Application of conventional, minimum variance distortionless response, and white-noise-constrained adaptive beamforming methods with ocean acoustic data collected by a single vector sensor illustrate an increase in spatial resolution but a corresponding decrease in beamformer output with increasing beamformer adaptivity. Expressions for the spatial coherence of all pairs of vector sensor components in homogeneous, isotropic noise show that significant coherence exists at half-wavelength spacing between particle motion components. For angular intervals about broadside, an equal spacing of about one wavelength for all components provides maximum directivity index, whereas each of the component spacings should be different to optimize the directivity index for angular intervals about endfire.

Robust beamforming using sensors with nonidentical directivity patterns

“…The latter can produce beampatterns which closely approximate a combination of monopole and dipole patterns but suffers from poor robustness which characterizes superdirectivity. 3 References [11] and [12] discuss covariance relations pertinent to the current and subsequent examples. 4 In this scenario, Ξ = 1 3×3 and Φ 0 = Φ dif is diagonal.…”

Performance of Line Arrays of Vector and Higher Order Sensors

“…4 illustrates the application of the beam pattern product theorem to an endfire steered line array at a frequency 2.5 times the nominal design frequency f0 at which the interelement spacing is one-half wavelength. The array consists of eight second order combined sensors.…”

Fabrication and Characterization of an Underwater Acoustic Tonpilz Vector Sensor for the Estimation of Sound Source Direction

“…[5,6] 단일 소자를 이용하여 벡터 센서로 응용한 연구로 는 Gordon et al [7] 이 2조각 낸 링 센서를 이용하여 쌍 극자 모드를 구현하는 방법을 연구한 이후, Butler et al [8,9] 이 링 세라믹을 8조각 낸 다음 이들을 적절히 조합하여 다중 모드를 구현하는 방법을 제안하고 이 것을 이용하여 외부 음원의 방향을 찾는 연구를 수행 한 바 있다. 유사한 원리에 의해 구형 벡터 센서를 구 현하는 연구로는 Ehrlich, [10] Ko et al, [11] Ko와 Pond, [12] Butler와 Ehrlich [13] 등의 연구 사례가 있다.…”