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Automatic tracking provides a critical and valuable component in the signal and information processing chain that provides a surveillance picture for military personnel. Multi-sensor fusion also provides benefits, though these are achieved provided a number of technical requirements are addressed. This paper identifies these in the context of undersea surveillance with active sonar towed and deployed...
The underwater acoustics research group at the Portuguese Naval academy has been working for some years on unsupervised classification of underwater sound [1-3]. Some software was developed using techniques developed by this group, but adapting the software developed during the research phase to the operational programs (that must be operated by less skilled personnel) proved to be difficult. So as...
High-frequency (HF) radars are operated in the 3-30 MHz frequency range and need to share the frequency bands with other radio services. Due to their over-the-horizon (OTH) capabilities, HF radars play an important role in remote sensing and surveillance. The propagation conditions of the electromagnetic wave depend on the earth's ionosphere and mailnly follow a daily cycle. Communication paths between...
In this paper, we present some results obtained with the Shadows system, the new synthetic aperture sonar, by IXSEA. First sections are a slight presentation where we expose the performances and specifications of Shadows. We present the results obtained on the lateral sonar by using first the algorithm of DPCA, second the simulation of DPCA parameters by using the navigation data. Hence we present...
The paper will consider the viability of exploiting the spatial diversity that exists in doubly-spread, underwater acoustic communications channels to provide enhanced capacity using an OFDM-MIMO system. The proposed method offers two forms of diversity. First, coded orthogonal frequency-division multiplexing (COFDM) provides frequency diversity by exploiting the frequency selectivity inherent in...
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