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.

High‐angular‐ and range‐resolution imaging using MIMO sonar with two‐dimensional deconvolution

“…Unlike the traditional imaging sonar, the multiple-input multiple-output (MIMO) sonar, using orthogonal waveforms and MFs, can produce a large-aperture virtual array, which ensures a higher angular resolution than its traditional singleinput multiple-output (SIMO) counterpart [12][13][14][15][16][17][18][19][20][21]. In terms of the angular resolution, in refs.…”

“…In terms of the angular resolution, in refs. [12][13][14][15][16] several high-angularresolution two-dimensional imaging methods using MIMO sonar or radar are proposed. In these methods, the high angular resolutions are mainly from the rational design of the transmitting and receiving MIMO arrays.…”

“…One may try the array and spectrum weighting to alleviate the spectrum leakage problem, yet it in turns reduce the angular and range resolutions. What's worse, the MIMO sonar always suffers from high range SLs produced by the cross-correlation functions (CCFs) between transmitting waveforms [12][13][14][15][16]. For practical application where non-ideal channel conditions are inevitable, CCFs always exist due to the imperfect orthogonality between waveforms, which will blur the outputted image of the MIMO sonar.…”

Improved high‐precision approach based on deconvolution in MIMO sonar imagery

“…In general, the MIMO imaging sonars proposed in this study employ the collocated mode. The performance of the target detection and localisation is enhanced when the MIMO technique is applied to sonar [3, 12–14].…”

“…Similar to the image resolution, the image definition is divided into the range dimension definition and angular dimension definition, both for the lower sidelobe levels. For the range definition, the MIMO sonar emits orthogonal waveforms with a wide band via all transmitting elements, and at the receiving end, the orthogonal waveforms are separated by matched filter echoes at each of the receiving elements [13,14]. The cosine window weighting of the matched filter is used to realise sidelobe suppression in the range dimension to enhance the definition [15][16][17].…”