Miniaturized frequency-diversity FPGA-DAS system for small-size object hydro-acoustic detection

Area of Science:

• Marine technology
• Oceanography
• Sensor systems

Background:

• Conventional Distributed Acoustic Sensing (DAS) systems require shore-based infrastructure, limiting their use in remote marine environments.
• There is a need for compact, low-power DAS solutions for open-sea monitoring, fisheries research, and underwater investigations.

Purpose of the Study:

• To develop a miniaturized, low-power DAS system capable of remote open-sea deployment.
• To achieve millihertz-level very low-frequency (VLF) response and reliable signal demodulation for underwater monitoring.

Main Methods:

• Utilized a field-programmable gate array (FPGA) for a miniaturized DAS system with low power consumption.
• Implemented frequency diversity to mitigate interference fading and a four-stage pipeline algorithm for real-time signal demodulation.
• Employed multi-domain clock homology to suppress low-frequency phase noise and isolated integrated packaging for thermal and vibration stability.

Main Results:

• The proposed DAS system demonstrated stable millihertz-level VLF response capability.
• Successfully captured diver movement signals (0.05-0.1 Hz) during a sea trial.
• Achieved diver detection and 1 mHz frequency response with a compact (less than A4 size) and low-power (30 W) system.

Conclusions:

• This miniaturized DAS technology offers a feasible solution for previously challenging remote open-sea monitoring applications.
• The system's small size, low power consumption, and high sensitivity advance capabilities in marine biological monitoring and underwater research.
• Represents a significant advancement in portable sensing for diverse underwater applications, including search and rescue.