Underwater communications testing of the multi-mode pipe projector
Keywords:Acoustic emission testing, Acoustic transducers, Acoustic wave transmission, Coastal zones, Global positioning system, Natural frequencies, Signal distortion, Barrel-stave projectors, Hyperbolic frequency modulated (HFM), Multi-mode pipe projector (MMPP), Underwater communications
AbstractThe functionalities of the multi-mode pipe projector (MMPP) as an underwater communications source, was investigated. The three transducer-equipped GPS buoys with its center frequency set for barrel-stave projector at 1500 Hz, MMPP at 1950 Hz and MMPP at 3850 Hz were deployed at testsite off the west coast of Florida in the Gulf of Mexico. Source levels were kept low so that acoustic emission did not exceed the maxima stated in the cruise plan and GPS NMEA data was encoded on hyperbolic frequency modulated (HFM) sweeps at a rate of 8 symbols per second. A group of type SSQ-53F (GPS) sonobuoys were laid to receive the GPS encoded acoustic signal and subsequently retransmit the data via RF link to CFAV Quest. It was observed that signals were received with high signal to noise ratio including 70 % clear and 26 % highly usable transmissions. Results shows that MMPP can be used in underwater communications as its performance is minimally impacted by multi-path distortion at range of 2km.
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