Nearfield target localization with a few snapshots for sonar array

Zhuo Li,Xiwei Guo,Deliang Liu,Peng He

doi:10.1186/s13638-018-1096-3

Abstract

Sonars can be used for detection of targets located on the sea floor where the signal undergoes multipath propagations which may arise large localization errors. Besides, underwater environment is often highly unstable so that a large number of snapshots which means long time sampling are not reliable. In sonar systems, the wideband chirp signals are usually used. This paper presents a nearfield target localization method for underwater environments. First, the time of arrival (TOA) and the direction of arrival (DOA) for nearfield wideband chirp signals are estimated with only a few snapshots by using the fractional Fourier transform (FRFT) and the SPICE algorithm. Then, the virtual station method which is proposed in our previous work is used so that the multipath problems can be converted into line-of-sight (LOS) problem and its Cramer-Rao lower bound (CRLB) is also analyzed. Finally, simulation results demonstrate the effectiveness of the proposed method.

Highlights

Sonar systems have been widely used for decades to detect an underwater target [1,2,3]
The active sonar transmits an acoustic signal at a predetermined interval and receives signals using a sensor array to find echoes that are reflected from a target, while the passive sonar which contains sensor array receives the acoustic signal which is transmitted from the target
We focus on wideband chirp, so the steering vector a(θk) depends on the time t, and the SPICE algorithm for narrowband signals cannot be applied directly to wideband signals

Summary

Introduction

Sonar systems have been widely used for decades to detect an underwater target [1,2,3]. In our previous work [11], a virtual station (VS) method has been proposed to solve the multipath problem and it will be directly used in this paper Another challenge emerges when the number of snapshots available for the estimation of the location parameters such as time of arrival (TOA) and direction of arrival (DOA) is limited. IAA, SLIM, and SPICE algorithms [12] are sparsity-based techniques that can estimate the DOA depending on a few snapshots with high resolution and low sidelobes They only apply to narrowband signals, because the steering vector of the received wideband signal model is time-variant. A joint TOA and DOA localization method for wideband chirp signals which is able to locate underwater targets with only a few snapshots is proposed.

Joint DOA and TOA estimation with a few snapshots

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Simulation results

Conclusions