Range-coherent matched field processing for low signal-to-noise ratio localization

Area of Science:

• Underwater acoustics
• Signal processing
• Array processing

Background:

• Conventional matched field processing (MFP) assumes random phase between snapshots.
• This assumption is problematic for moving sources due to unknown motion and frequency imprecision.
• Existing methods struggle with localizing low signal-to-noise ratio (SNR) sources.

Purpose of the Study:

• To introduce and validate range-coherent matched field processing (MFP) for localizing moving underwater acoustic sources.
• To demonstrate the method's effectiveness in low SNR conditions.
• To leverage synthetic aperture principles for enhanced source localization.

Main Methods:

• Range-coherent MFP coherently combines snapshots by determining the source phase acquired between them.
• Applies MFP to the cross-spectrum of time-separated snapshots.
• Incorporates source velocity into the MFP search space, forming a passive synthetic aperture.

Main Results:

• Range-coherent MFP provides robust velocity estimates at low SNR.
• Enhanced pre-processing and synthetic aperture gain significantly reduce the required signal level for localization.
• Successfully localized a previously undetectable faint source in the SWellEx-96 experiment data.

Conclusions:

• Range-coherent MFP offers a significant advancement for localizing faint, moving underwater acoustic sources.
• The method overcomes limitations of conventional MFP by accounting for source motion and phase.
• Demonstrates superior performance in challenging low SNR acoustic environments.