The current generation of high-frequency active 3-D acoustic imaging systems presents a challenge to the covert use of Underwater Vehicles (UVs) by Special Forces teams. An acoustic intercept capability is needed to detect active signals before the UV is detected, so that it can vector away from the source. The team of Advanced Acoustic Concepts and Montana State University propose to design and prove the feasibility of an acoustic intercept sensor system based on sparsely populated volumetric array technology. The system will measure bearing with a minimum of 15 degrees of accuracy and will cover a frequency range of 10-512 kHz, while remaining with the strict power and weight requirements for use on a UV. Using the sparse array concept, the signal processing load can be kept to a minimum, allowing weight and power to fit within the required 15 lbs dry weight and 25 W constraints. MSU will leverage its expertise in low power embedded processing to prove the feasibility of using a Field Programmable Gate Array to implement a low power integrated solution using a system-on-a-chip approach that meets AACs acoustic intercept processing needs.
Benefit: The sparsely populated volumetric array technology lends itself ideally to a lower power and light acoustic intercept application because the sensor can be very compact and the processing load can be very small compared to fully-filled volumetric arrays and larger sensor systems that rely on beamforming. Because the sparse array-based system does not beamform, much smaller and lower power processors can be used. The sparse array technology allows a compact sensor to measure bearing and elevation over a very large frequency range, while most acoustic intercept systems are limited to one or two of these traits. The proposed acoustic intercept system can be deployed on any type of UV, including Unmanned Underwater Vehicles (UUVs), and would be ideal as a passive reacquisition system for port security systems such as the In-harbor Ship Defense system that AAC is developing under a separate SBIR project. Once a target is detected via a long-range active system, a small mobile unit such as a RHIB or unmanned surface vehicle can be sent out to intercept the threat, but will need a passive bistatic receive capability like the acoustic intercept sensor to reacquire the target. AAC will also explore Homeland Security applications for port security and waterside asset protection, since a light, compact, low-power, and low-cost sensor that can cover high frequencies will be very useful for underwater threat detection, including diver detection.
Keywords: acoustic sensor, passive sensor, Signal processing, Sonar, sparse array, acoustic intercept, FPGA
