Localizing Strong Scatterers of Very Low Frequency Electromagnetic Waves Using Phase and Polarization Information
Abstract
Goal The goal of this Phase II Imaging Through Almost Anything (ITA3) effort is to recover coordinates of strong scatterers from measurements of scattered and also total (=incident + scattered) electromagnetic fields where the carrier frequency is no more than 30 kHz. Current Practice Very low frequencies (VLF) have extremely long wavelengths exceeding 10 km, so the diffraction limit implies at best 5 km image resolution. However, with such long wavelengths, most scatterers are in the near field of the detector and the diffraction limit does not apply. There are many sources of opportunity of these VLF waves, for example from lightning. Accurate near field measurements can provide much higher resolution information. Impact Rather than reconstructing an N2 image or N3 volume, we tackle a far simpler problem of determining the three spatial coordinates of each strong scatterer. Scattering targets could be land mines, tanks, barrels, or even airborne missiles. If we can successfully detect scattered fields from plane waves incident on these targets, then passive monitoring of scatterer positions could be covert. Rather than use background plane wave sources, local sources, such as dipole and/or loop antennae would generate stronger signals and could be used for noninvasive inspection whenever overt operation is acceptable, such as for container and vehicle inspection. Extending the proposed approach to a local dipole source should be reasonable but extending to loop antennae could be difficult.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Oct 18, 2018
- Source ID
- HR00111910002
Entities
People
- Sarah Patch
Organizations
- Defense Advanced Research Projects Agency
- University of Wisconsin System