Browsing Reprints by Issue Date
Now showing items 221-240 of 548
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Source localization for a low frequency active multistatic sonar system
(NATO. SACLANTCEN, 1993/08)In a low frequency active bistatic or multistatic sonar system, it is essential tohave accurate knowledge of the location of the transmitting source ship. Inaccuracies inthis information translate directly to errors in the ... -
Array and cable tracking data through ship maneuvers
(NATO. SACLANTCEN, 1993/08)This paper presents tracking results from two sea tests in which a towed cable and array were tracked at the Atlantic Undersea Test and Evaluation Center (AUTEC). The tracking tests involved instrumenting the cable with ... -
A shallow water system for maximizing echo to reverberation ratio
(NATO. SACLANTCEN, 1993/08)A method for increasing incident energy on mid-depth targets while at the same range reducing boundary reverberation for shallow water ducts has been devised. The basis of the approach is couched in range dependant normal ... -
Channel-adapted source for shallow water
(NATO. SACLANTCEN, 1993/08)In shallow water areas the utilization of active sonar is complicated by the fact that in these environments the performance of active systems is degraded by source signal interaction with channel boundaries. These boundary ... -
Low frequency active sonar (LFA) bottom loss requirements
(NATO. SACLANTCEN, 1993/08)A bottom interaction simulator was developed to investigate LFA bottom bounce losses, i.e., the mismatch losses, which occur in matched filter processing of bottom and target reflected signals due to the time spreading ... -
Comparison of measured reverberation on the transmission loss data with modelled results on the West Florida continental shelf
(NATO. SACLANTCEN, 1993/08)Acoustic data from the September, 1992 Area Characterization Test (ACT I) are compared to ADAM (Advanced Development Acoustic Model) output. Conduct of harsh shallow water acoustic exercises, and data interpretation mandates ... -
Array shape determination with a real-time model
(NATO. SACLANTCEN, 1993/08)A shape estimation scheme based on precomputed frequency-domain solutions of array motion is presented. The boundary conditions supporting each solution are discrete Fourier transform (OFT) components of sensor measurements, ... -
Achievable signal gains for line arrays in shallow water
(NATO. SACLANTCEN, 1993/08)The well-documented conformance of signal gain to a 20 log n relationship for deep water, refracted paths, does not apply to shallow water where angular spreading effects from boundary roughness limit the signal gains that ... -
Surface duct propagation loss measurements and model predictions at low and mid frequencies
(NATO. SACLANTCEN, 1993/08)Side-by-side measurements of low- and mid-frequency propagation loss were obtained during a sea test conducted in the North Atlantic during February of 1992. These measurements are compared to each other and with model ... -
Effect of different bandwidths for the detection of extended targets in reverberation
(NATO. SACLANTCEN, 1993/08)In this paper, firstly the theoretical background of bandwidth effects on detection in noise and reverberation is presented in some detail, and secondly the relevant results of sea. trials with a low frequency active sonar ... -
The Response model: an operational model for towed array shape and attitude estimation validated on TABAT data
(NATO. SACLANTCEN, 1993/08)An operational model for array shape and attitude estimation, based on the continuous measurement of heading and depth at a single position in the array, is presented. This model, which we call the Response model has been ... -
Correlation of backscatter with bottom topography
(NATO. SACLANTCEN, 1993/08)Practical data from low frequency sonar operations in shallow water has been analysed to demonstrate that a high degree of correlation exists between the received signal due to bottom hackscattering and the hottom gradient ... -
Practical active sonar receiver systems using fast frequency-domain correlation
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Real time-frequency active sonar processing: a massively parallel approach
(NATO. SACLANTCEN, 1993/08)A paradigm for massively parallel processing of matched filters, replica correlators, ambiguity functions and time-frequency distributions using an SIMD (Single Instruction Multiple Data) programming methodology is presented. ... -
Environmental impact on mobile sonar shallow water operations
(NATO. SACLANTCEN, 1993/08)Shallow Water operations provide unique challenges for mobile sonars. In many cases propagation conditions can be optimized - our studies have shown that sound channeling can occur in approximately 75% of the strategic ... -
Low frequency resonance backscatter from near-surface bubble clouds
(NATO. SACLANTCEN, 1993/08)When active sonar systems are used to insonate the sea surface, anomalous scattering is observed in the form of enhanced backscatter, and more importantly, in the form of discrete, bright echoes. The most plausible explanation ... -
On the physics and design of electrical discharge sources for active undersea surveillance
(NATO. SACLANTCEN, 1993/08)Underwater electrical arcs have long been used as an impulsive sound source, although efforts to improve efficiency and control acoustic output have been limited by inadequate understanding of the arc initiation process. ... -
Statistical characterization of shallow-water bistatic sonar reverberation and noise
(NATO. SACLANTCEN, 1993/08)Shallow-water, low-frequency bistatic sonar measurements often exhibit high noise caused by bathymetric reverberation and other sources. Understanding the noise statistics is an essential first step in developing filters ... -
About the effective Doppler sensitivity of certain nonlinear chirp signals (NLFM)
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Considerations related to warfare system design and operation of tactical platforms in a low- frequency active sonar environment
(NATO. SACLANTCEN, 1993/08)Low-Frequency Active Sonar System (LFASS) can provide significant improvements in the detection, localization and classification of very quiet submarine contacts. Achievement of the predicted performance improvements will ...