Hybrid phase shift and shifted sideband beamforming for large‐aperture MIMO sonar imaging

Abstract

A multiple‐input multiple‐output (MIMO) sonar can form a large‐aperture virtual uniform linear array (ULA) from a small number of physical elements. However, the large‐aperture MIMO sonar encounters a dilemma between the computation load and the imaging performance. Since the traditional phase‐shift beamformer (PSBF) and shifted sideband beamformer (SSBF) cannot solve the dilemma individually, the authors proposed a hybrid beamformer (HBF) which combines PSBF and SSBF together. Specifically, the proposed HBF contains the off‐ and on‐line processing. In the off‐line processing SSBF is applied to the transmitting ULA to process transmitting waveforms. In the on‐line processing PSBF is applied to the receiving ULA, and outputs of off‐line SSBFs are utilised to matched filter outputs of PSBFs. Thus, in the proposed HBF the time delays of SSBF is calculated off‐line; and the multi‐beam processing is simplified as PSBFs on the receiving ULA. Consequently, the proposed HBF can reduce the computation load of the large‐aperture MIMO sonar effectively while obtaining a fine imaging performance. Numerical simulations show the effectiveness of the proposed HBF.

Keywords

• hybrid phase shift beamforming
• hybrid shifted sideband beamforming
• large‐aperture MIMO sonar imaging
• multiple‐input multiple‐output sonar
• large‐aperture virtual uniform linear array
• large‐aperture virtual ULA