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60 MTR June 2011 products Marport Deep Sea Technologies Inc. introduces AquaPix, a new interferometric Synthetic Aperture Sonar targeted to mine countermeasures, hydrography, seabed survey and other underwater imaging markets. AquaPix is the latest product to be based on Marport’s Software Defined Sonar, an underwater acoustics technology plat- form that enables advanced underwater sensing, commu- nications and imaging products. The sonar is frequency agile from 200 – 400 kHz and offers range independent resolution of 2.5cm by 2.5cm with co-registered 3D bathymetry. Effective swath widths are up to 12 times water depth in shallow water, to a maximum width of 600m. With the integration of AquaPixonboard AUVs the system can reconstruct images taking advantage of sonar sensor data with multi-aspect diversity. It’s expected that a future application of AquaPix will be Circular Synthetic Aperture Sonar (CSAS) using techniques simi- lar to medical imaging to reconstruct scenes of interest from data obtained over a full circular aperture. Such advanced imaging capabilities will provide the critical level of image detail required in missions such as under- water ISR, mine countermeasures, hydrographic survey and search and recovery. The AquaPix sonar design exploits a dual row frequency multiplexed transducer array which allows selection of the vertical beam width of both the transmitter and the receiver on the fly in order to optimally suppress multi- path. Two beams with different beam-widths are trans- mitted at the same time, at different frequencies, and the best beam is dynamically selected by frequency filtering, a technique which is directly inspired from Orthogonal Frequency Division Multiplexing (OFDM) used in radio communications for the same purpose. At the same time the multiplex provides the high level of spatial overlap required to robustly implement the adaptive focusing techniques referred to above. The AquaPix sonar solution is modular in design, using broadband piezocomposite ceramic arrays which are fully encapsulated for robustness against harsh environments. The use of piezocomposite ceramics not only provides unsurpassed bandwidth and flexibility, but also delivers repeatability in manufacture of sonar arrays with precisely defined beam patterns to provide the spatial filtering cru- cial to achieving high performance. Transmit and receive electronics are fully encapsulated within the sonar array modules, with small, flexible cables for connectivity to a host pressure vessel. The pre-amplifiers and sampling rates exploit many years of SAS science and engineering development and achieve true 24 bit sampling with a power consumption of 150mW per channel. The transmit electronics achieve 97% efficiency, with fine phase and amplitude control. The modular arrays are designed to be integrated into a range of platforms such as autonomous underwater vehi- cles, towed vehicles and hull mounts. www.marport.com Synthetic Aperture Sonar
