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Processing Continuous Active Sonar Transmissions to Achieve an Arbitrarily Fast Update Rate With Full Instantaneous Bandwidth
A processing technique for continuous active sonar (CAS) that uses linear frequency modulation (LFM) waveforms is presented. LFM CAS employs wideband long-duration LFMs with 100% transmit duty cycle. The received signals are typically processed in sub-bands by forming a sequence of matched-filter replicas that correspond to consecutive segments of the full waveform; this increases the update rate ...Show More
Striation Processing of Data From the 2013 Target and Reverberation Experiment (TREX13)
In active sonar processing, the discrimination of the target versus clutter can be a significant challenge. Whereas conventional processing often uses target kinematics to limit the possible target tracks, it has recently been shown that frequency domain information (based on the waveguide invariant principle) can also be incorporated to further limit the possible target tracks in an environmental...Show More
Parabolic Equation Methods for Terahertz 3-D Synthetic Aperture Imaging
Terahertz (THz) imaging has shown great potential for nondestructive evaluation of a wide variety of manufactured products composed of nonpolar dielectric materials. Recent work by the authors and others has demonstrated the ability to produce three-dimensional (3-D) THz tomographic images of such objects using a single dataset collected in a 2-D synthetic aperture configuration. However, the irre...Show More
Acoustic propagation in the ocean waveguide is characterized by mutual interference between the multiple ray paths connecting a source-receiver pair. In the Russian literature, these interference effects have been distilled mathematically into a single parameter, the so-called waveguide invariant defined as beta. The conventional wisdom is that the numerical value of beta is negative in deep water...Show More
Terahertz scattering from contaminants embedded in textile rope and sling materials
2015 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium)
Year: 2015 | Conference Paper |
Terahertz Time Domain Imaging (THz-TDI) is a new technology that is rapidly being explored by researchers around the world with particular interest in non-destructive evaluation (NDE) applications for manufacturing, security screening, and medical imaging. This work expands the scope of THz NDE by investigating its potential as a new and innovative method for NDE of nylon ropes and slings, which a...Show More
Previous work has shown that the waveguide invariant can provide a new physics-based tracking constraint that exploits the multipath structure to limit the possible target tracks in pulsed active sonar (PAS) data. The innovation of the invariance extended Kalman filter (IEKF) tracking algorithm is to make predictions and measurements of the target's propagation signature in addition to the convent...Show More
Terahertz non-destructive sensing of layered materials with curved surfaces
2015 16th International Radar Symposium (IRS)
Year: 2015 | Conference Paper |
Terahertz (THz) imaging has shown great potential for nondestructive evaluation (NDE) of a wide variety of manufactured products. Its ability to penetrate many non-polar dielectrics allows tomographic imaging of an object's 3D structure. The authors' previous work demonstrated the ability to produce 3D THz tomographic images of objects using a single data set collected in a 2D synthetic aperture c...Show More
Terahertz Non-destructive Evaluation of Layered Media with the Maximum Likelihood Estimator
2014 International Symposium on Optomechatronic Technologies
Year: 2014 | Conference Paper |
Cited by: Papers (1)
Terahertz (THz) non-destructive evaluation (NDE) has shown great promise for applications in manufacturing, security screening, and medical imaging. However, interpretation of the THz A-scans is complicated by a number of factors. Other researchers have applied signal processing techniques that improve object boundary detection, but still rely on human interpretation without a statistical framewor...Show More
Terahertz Non-destructive Evaluation of Textile Ropes and Slings
2014 International Symposium on Optomechatronic Technologies
Year: 2014 | Conference Paper |
Cited by: Papers (2)
Terahertz (THz) technology has shown great promise for non-destructive evaluation (NDE) applications in manufacturing, security screening, and medical imaging. This work expands the scope of THz NDE, demonstrating its use as a new and innovative method for NDE of nylon ropes and slings. The strength of ropes and slings is compromised when grains of sand or sea salt become deeply embedded between t...Show More
Depth-based passive tracking of submerged sources in the deep ocean using a vertical line array
2013 Asilomar Conference on Signals, Systems and Computers
Year: 2013 | Conference Paper |
Cited by: Papers (8)
Vertical line arrays (VLAs) deployed below the critical depth in deep ocean environments have been shown to have lower levels of distant shipping noise [1]. In addition, acoustic energy from nearby targets travels via the Reliable Acoustic Path (RAP), and thus has an enhanced signal level. The combination of these two factors produces a favorable detection scenario. However, nearby surface ship in...Show More
THz non-destructive evaluation using correlation processing
2013 38th International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz)
Year: 2013 | Conference Paper |
Terahertz (THz) has been well known for its unique ability to propagate through non-polar packaging material. At the same time, THz wavelengths are small enough to provide meaningful imaging resolution, leading to their large potential in non-destructive evaluation. Correlation processing is a technique that has been shown to detect phase resonances in illicit chemicals, and in this paper, is exte...Show More
Terahertz Spectral Imaging Using Correlation Processing
Terahertz (THz) reflection imaging has the potential to extract unique spectral signatures from various materials of interest, but these signatures can be distorted by rough surface scattering, low signal strength, and alignment errors. One method of addressing these challenges and increasing performance is to coherently combine reflection information across frequency bands. This method, called co...Show More
Terahertz spectral imaging using correlation processing
2012 37th International Conference on Infrared, Millimeter, and Terahertz Waves
Year: 2012 | Conference Paper |
Cited by: Papers (1)
Terahertz (THz) reflection spectroscopy has the potential to extract unique spectral signatures from various materials of interest, but these signatures can be distorted by rough surface scattering, low signal strength, and alignment errors. One method of addressing these challenges and increasing gain is to coherently combine information across frequency bands. This method, called correlation pro...Show More
3-D broadband terahertz synthetic aperture imaging
2012 37th International Conference on Infrared, Millimeter, and Terahertz Waves
Year: 2012 | Conference Paper |
Cited by: Papers (2)
3-D imaging at terahertz (THz) frequencies provides a capability for a number of applications, such as explosives detection and non-destructive evaluation. Many current 3-D techniques require mechanical scanning, and often lack spectral resolution required for chemical detection. In this paper, 3-D broadband synthetic aperture imaging techniques are demonstrated by imaging familiar objects with a ...Show More
Model-Based Material Parameter Estimation for Terahertz Reflection Spectroscopy
One important yet commonly overlooked phenomenon in terahertz (THz) reflection spectroscopy is the etalon effect-interference caused by multiple reflections from dielectric layers. Material layers are present in many THz applications from the monitoring of pharmaceutical tablet coating thickness to the detection of drugs, explosives, or other contraband concealed beneath layers of packaging and/or...Show More
Extraction of time-frequency target features
Tobias G. Oesterlein;Chensong He;Jorge E. Quijano;Richard L. Campbell;Lisa M. Zurk;Martin Siderius
2010 Conference Record of the Forty Fourth Asilomar Conference on Signals, Systems and Computers
Year: 2010 | Conference Paper |
Cited by: Papers (6)
Physics-based detection algorithms can improve discrimination of sonar targets from competing bottom reverberation, but are vulnerable to environmental uncertainties. Recent research in the underwater community has identified an environmentally robust time-frequency signature for improved target discrimination. Application of this “invariant” requires processing algorithms to identify striations i...Show More
The waveguide invariant has been widely studied and applied in the context of shallow water passive sonar. The invariant provides a simple linear relationship between the frequency content of a moving broadband source and the propagation range, and this relationship is not generally sensitive to small variations in environment parameters. Recent research has shown that a similar structure can be o...Show More
In passive sonar systems, knowledge of low-frequency shipping noise is significant for target detection performance. However, an accurate model for the shipping noise structure is difficult to obtain, because of the varying distributions of ships and complicated underwater environment. This work characterizes low-frequency distant shipping noise observed in deep water environments as a function of...Show More
This paper investigates the system requirements and signal processing tools for a semi-autonomous passive acoustic boat detection framework for monitoring marine environments. The objective is to develop a surveillance system which provides wide area coverage, automatic (boat) detection, and ultimately the ability to communicate real-time alerts (i.e., a bell-ringer system). A critical challenge f...Show More
Modeling acoustic scattering from the seabed using transport theory
OCEANS 2010 MTS/IEEE SEATTLE
Year: 2010 | Conference Paper |
Radiative Transfer (RT) theory has established itself as an important tool for electromagnetic remote sensing in parallel plane geometries with random distributions of scatterers, and most recently it has also been proposed as a model for the propagation of elastic waves in layered ocean sediments. In this work the capabilities of this model are illustrated, as the RT method is used to predict bac...Show More
Utilizing parallel plate waveguide modes for terahertz sensing
F. Kernan;M. Wachsmuth;J. Higgins;B. Pejcinovic;L. Zurk;R. Campbell
35th International Conference on Infrared, Millimeter, and Terahertz Waves
Year: 2010 | Conference Paper |
Parallel-plate waveguide sensors are investigated by characterizing TM and TE modes when filled with inhomogeneous and homogeneous samples. Effects of multi-mode TE propagation within PPW and radiation patterns are investigated. Lactose detection is demonstrated by TDS and CW-VNA techniques.Show More
Modeling Rough-Surface and Granular Scattering at Terahertz Frequencies Using the Finite-Difference Time-Domain Method
Exploration of the terahertz (THz) portion of the electromagnetic spectrum has recently expanded due to advances in ultrafast optical laser systems. The application of THz imaging to detect explosive materials (and other chemical agents) is a promising potential application because of the unique spectral signatures found for many explosives in the THz band. However, since the wavelength of THz rad...Show More
Enhanced Kalman Filter Algorithm Using the Invariance Principle
Target tracking in multistatic active sonar systems is often limited in shallow-water environments due to the high level of bottom reverberation that produces false detections. Past research has shown that these false alarms may be mitigated when complete knowledge of the environment is available for discrimination, but these methods are not robust to environmental uncertainty. Recent work has dem...Show More
Application of Radiative Transfer Theory to Acoustic Propagation in the Ocean Bottom
OCEANS 2007
Year: 2007 | Conference Paper |
Acoustic scattering from the ocean bottom has been extensively studied by applying analytical methods based on the wave equation. This has the advantage of being mathematically rigorous but many of these techniques are not applicable for complex sediment environments with combined volume and rough surface scattering. In this research, the use of the radiative transfer (RT) theory is explored as a ...Show More
Application of Radiative Transfer Theory to Acoustic Propagation in the Ocean Bottom
Year: 2007 | Conference Paper |
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