Frequency Domain Electromagnetic Sensor Array Development
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Author | : |
Publisher | : |
Total Pages | : 24 |
Release | : 2007 |
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A laboratory prototype frequency domain electromagnetic induction sensor array suitable for simultaneous operation with an array of cesium vapor total field magnetometers has been designed and fabricated and has undergone limited bench testing. The design is based on the GEM-3 active primary field cancellation technology, which creates a "magnetic cavity" for each receive coil in the array. The array's magnetometers would be mounted inside the receive coils, within the magnetic cavities. This is very important because the primary transmit field would otherwise be strong enough to shift the total magnetic field vector (static magnetic field plus EMI components) outside the operating envelope of the magnetometers. Because the array configuration does not have the symmetry of a standard GEM-3, in-phase drift tends to be more severe. Tests with the prototype array show drift rates roughly one order of magnitude larger than with a standard GEM-3. However, demedian filtering such as that used for the MM-0033 towed GEM-3 array can correct for the drift. The most serious issue for the array is structural rigidity. When the array is bent, the bucking coils do not properly cancel the field from the outer transmit loop. Calculations indicate that bucking errors amounting l0's of ppm can be caused by bending the array by a few tenths of a degree over a distance of about 30 cm. The array would have to be held stiff to this sort of tolerance. For towed applications on land this may be difficult because the array will be subjected to significant bending stresses as it is towed over any realistic terrain. The bouncing and jostling motions for vehicle towed systems tend to have scales comparable to those of buried UXO signals. The situation may not be so serious for marine applications where the array would be buoyed up and not subject to such severe stresses.
Author | : |
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Total Pages | : 19 |
Release | : 2002 |
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The Chemistry Division of the Naval Research Laboratory has developed the Multi-sensor Towed Array Detection System for use in unexploded ordnance detection and classification. With support from the Environmental Security Technology Certification Program, we are developing a frequency-domain electromagnetic induction sensor array to extend our capabilities. The first task in this program is to characterize the commercial GEM-3 sensor and assess its suitability for use in a towed array. In this report, we detail our characterization results and note the problems we encountered. We conclude by listing the modifications to the baseline sensors that we will make for the array we will field.
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Publisher | : |
Total Pages | : 76 |
Release | : 2007 |
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ISBN | : |
The Chemistry Division of the Naval Research Laboratory has developed the Multi-sensor Towed Array Detection System for use in unexploded ordnance detection and discrimination. With support from the Environmental Security Technology Certification Program, we have developed a frequency-domain electromagnetic induction sensor array to extend the discrimination capabilities of the MTADS. We have demonstrated the system at the Standardized UXO Demonstration sites at Aberdeen Proving Ground, MD and Yuma Proving Ground, AZ. At each of the sites, we surveyed the Calibration Lanes, the Blind Test Grid, and as much of the Open Field Area as possible. In this report, we describe the sensors demonstrated, show examples of the data collected, describe our analysis methodologies, and report the detection and discrimination results as scored by management of the test sites and analysts from the Institute for Defense Analyses.
Author | : Misac N. Nabighian |
Publisher | : SEG Books |
Total Pages | : 989 |
Release | : 1988 |
Genre | : Electromagnetic fields |
ISBN | : 1560800224 |
As a slag heap, the result of strip mining, creeps closer to his house in the Ohio hills, fifteen-year-old M. C. is torn between trying to get his family away and fighting for the home they love.
Author | : Mesut Gökten |
Publisher | : Springer Nature |
Total Pages | : 124 |
Release | : 2022-06-01 |
Genre | : Technology & Engineering |
ISBN | : 3031017145 |
In this book, a general frequency domain numerical method similar to the finite difference frequency domain (FDFD) technique is presented. The proposed method, called the multiresolution frequency domain (MRFD) technique, is based on orthogonal Battle-Lemarie and biorthogonal Cohen-Daubechies-Feauveau (CDF) wavelets. The objective of developing this new technique is to achieve a frequency domain scheme which exhibits improved computational efficiency figures compared to the traditional FDFD method: reduced memory and simulation time requirements while retaining numerical accuracy. The newly introduced MRFD scheme is successfully applied to the analysis of a number of electromagnetic problems, such as computation of resonance frequencies of one and three dimensional resonators, analysis of propagation characteristics of general guided wave structures, and electromagnetic scattering from two dimensional dielectric objects. The efficiency characteristics of MRFD techniques based on different wavelets are compared to each other and that of the FDFD method. Results indicate that the MRFD techniques provide substantial savings in terms of execution time and memory requirements, compared to the traditional FDFD method. Table of Contents: Introduction / Basics of the Finite Difference Method and Multiresolution Analysis / Formulation of the Multiresolution Frequency Domain Schemes / Application of MRFD Formulation to Closed Space Structures / Application of MRFD Formulation to Open Space Structures / A Multiresolution Frequency Domain Formulation for Inhomogeneous Media / Conclusion
Author | : Mesut Gokten |
Publisher | : Morgan & Claypool Publishers |
Total Pages | : 137 |
Release | : 2012 |
Genre | : Science |
ISBN | : 1627050159 |
Presents a general frequency domain numerical method similar to the finite difference frequency domain (FDFD) technique. The objective of developing this new technique is to achieve a frequency domain scheme which exhibits improved computational efficiency figures compared to the traditional FDFD method.
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Total Pages | : 0 |
Release | : 1998 |
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This report includes results on the applications of time frequency distributions in blind source separation and direction finding problems. A novel approach based on time-frequency distributions (TFDs) for separating signals received by a multiple antenna array is developed. The sources have different time-frequency signatures and are instantaneously mixed at the array sensors. The proposed approach provides a significant improvement in performance over the recently introduced spatial time-frequency distributions, specifically for signals with close time-frequency signatures. Spatial averaging of the TFDs of the sensor data is performed to eliminate the interactions of the sources signals in the time-frequency domain, and as such restores important properties of the source TFD matrix. We have also improved nonstationary source signal estimation by performing the blind source separation using ambiguity functions, and as such, avoid the inclusion of cross-terms in the estimation process. Our third contribution to this area is the introduction of the Time-Frequency MUSIC as a new array signal processing method based on time-frequency signal representations. This report also includes contributions to problems of fast computation TFDs, spatial processing for frequency diversity spread spectrum communications as applied to partial jamming mitigation, and subband array processing to combat fading and multipath.
Author | : Prabhakar S. Naidu |
Publisher | : CRC Press |
Total Pages | : 478 |
Release | : 2000-07-06 |
Genre | : Technology & Engineering |
ISBN | : 9780849311956 |
Sensors arrays are used in diverse applications across a broad range of disciplines. Regardless of the application, however, the tools of sensor array signal processing remain the same. Furthermore, whether your interest is in acoustic, seismic, mechanical, or electromagnetic wavefields, they all have a common mathematical framework. Mastering this framework and those tools lays a strong foundation for more specialized study and research. Sensor Array Signal Processing helps build that foundation. It unravels the underlying principles of the subject without reference to any particular application. Instead, the author focuses on the common threads that exist in wavefield analysis. After introducing the basic equations governing different wavefields, the treatment includes topics from simple beamformation, spatial filtering, and high resolution DOA estimation to imaging and reflector mapping. It studies different types of sensor configurations, but focuses on the uniform linear and circular arrays-the most useful configurations for understanding array systems in practice. Unique in its approach, depth, and quantitative focus, Sensor Array Signal Processing offers the ideal starting point and an outstanding reference for those working or interested in medical imaging, astronomy, radar, communications, sonar, seismology-any field that studies propagating wavefields. Its clear exposition, numerical examples, exercises, and wide applicability impart a broad picture of array signal processing unmatched by any other text on the market.
Author | : |
Publisher | : |
Total Pages | : 704 |
Release | : 1995 |
Genre | : Aeronautics |
ISBN | : |
Author | : Joseph Shiloh |
Publisher | : Springer Science & Business Media |
Total Pages | : 452 |
Release | : 2007-05-08 |
Genre | : Technology & Engineering |
ISBN | : 0306470934 |
In the tradition of the previous three conferences, the proceedings of the 4th Ultra-Wideband Short-Pulse Electromagnetics Conference explores topics including pulse generation and detection; broadband electronic systems; antennas - theory, design, experiments and systems; pulse propagation; scattering theory; signal processing; and buried targets - detection and identification.