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Ingen bildrubrik

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Ingen bildrubrik

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    4. Field experiment

    5. Time series and power spectrum, boat at 3000 rpm

    6. Boat running at a speed of 18 knots, channel 1,3 and 4

    7. Boat running at a speed of 18 knots, channel 1,3 and 4

    8. Multipath Characterization of Hydroacoustic Signals by Autocoherence Estimation Leif Persson*, John W.C. Robinson� and Melvin J. Hinich+ *National Defence Research Establishment FOA, S172 90 Stockholm, Sweden. Also at Dep. of Seismology, Uppsala University, S-75002 Uppsala, Sweden. � National Defence Research Establishment FOA, S172 90 Stockholm, Sweden. + Applied Research Laboratories, The University of Texas at Austin. P.O. 8029, Austin, TX, 78713-8029.

    9. Definitions 1: Bicoherence Estimation

    14. We use bicoherence analysis for identification of source frequencies. Bearing and range estimation of C-W narrow-band sonar-signals are difficult in shallow water . Spatial filtering and smoothing in sonar array processing reduce the temporal and spatial resolution. We use autocoherence as a measure for multipath analysis on real data generated by a small boat in the Baltic sea.

    19. Conclusions We use bicoherence for identification of source frequencies prior multipath analysis. We use autocoherence as a measure for quantify the level of multipath. At longer distances (i.e. >300m) the autocoherence is relatively large. At shorter distances (i.e. <300m) the autocoherence decreases as the boat approach the sonar.

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