Ramp response signatures for dielectric targets

Soumya Nag; Leon Peters Jr.

doi:10.1117/12.324243

4 September 1998 Ramp response signatures for dielectric targets

Soumya Nag, Leon Peters Jr.

Proceedings Volume 3392, Detection and Remediation Technologies for Mines and Minelike Targets III; (1998) https://doi.org/10.1117/12.324243
Event: Aerospace/Defense Sensing and Controls, 1998, Orlando, FL, United States

Abstract

The scattered field from a ramp driving function traces out the transverse cross sectional area profile of a metallic target as a function of time or depth of the target. This concept has been used in the past to generate 'low frequency' images of simple conducting shapes. This concept is currently being examined for dielectric scatterers such as land mines. It has been applied to theoretically computed scattered fields of dielectric spheres and to experimentally measured scattered fields from dielectric targets in free space. There are some advantages to applying this technique to identify land mines. First, the ramp response yields information about target size, orientation and geometrical shape. Second, the early time component of the scattered fields used in this imaging concept is relatively strong as contrasted to the late time response used for resonant target identification. Third, it is a low frequency concept since the ramp response frequency spectrum is proportional to the impulse response spectrum weighted by the inverse of the frequency squared. This is significant since the attenuation in most earth at a given depth increases as frequency increases for the frequency bandwidth used to detect land mines. However, for dielectric targets, the critical angle and internal scattering mechanisms can change the ramp response from their transverse cross sectional areas versus distance. Physical Optics solutions for the ramp response of dielectric spheres have been obtained and have been compared with their corresponding eigen function solutions. For a dielectric target, a way to improve the ramp response in the presence of the internal specular scattering mechanisms has been discussed. Also the ramp response signatures of some dielectric targets including a land mine kept in free space have been extracted from measured data for broadside and endfire excitations.

Citation Download Citation

Soumya Nag and Leon Peters Jr. "Ramp response signatures for dielectric targets", Proc. SPIE 3392, Detection and Remediation Technologies for Mines and Minelike Targets III, (4 September 1998); https://doi.org/10.1117/12.324243

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