The idea of using acoustically induced Doppler spectra as a means for target detection and identification is introduced. To demonstrate feasibility of such a technique, an analytical solution for the calculation of the bistatic scattered Doppler spectrum from an acoustically excited, vibrating dielectric circular cylinder is presented. The incident plane wave is assumed to be polarized along the axis of the cylinder. A perturbation method is developed to calculate the electromagnetic scattering from a slightly deformed and inhomogeneous dielectric cylinder. Then, assuming the vibration frequency is much smaller than the frequency of the incident electromagnetic wave, a closed form expression for the time-frequency response of the bistatic scattered field is obtained. The solution for acoustic scattering from a solid elastic cylinder is applied to give the displacement on the surface as well as the compression and dilation within the cylinder. Both the surface displacement and the variation in material density within the cylinder contribute to the Doppler component of the of the electromagnetic scattered field. Results indicate that the scattered Doppler frequencies correspond to the mechanical vibration frequencies of the cylinder, and the sidelobe Doppler spectrum level is, to the first order, linearly proportional to the degree of deformation and is a function of bistatic angle. Moreover, the deformation in the cylinder, and thus the Doppler sidelobe level, only becomes sizeable near frequencies of normal modes of free vibration in the cylinder. These resonant frequencies are found to depend only on the object properties and are independent of the surrounding medium. Utilizing the information in the scattered Doppler spectrum could provide an effective means of buried object identification, where acoustic waves are used to excite the mechanical resonances of a buried object.
Acoustic and electromagnetic wave interaction: a technique for detection of buried objects
2000
9 Seiten, 14 Quellen
Conference paper
English
Detection of buried objects using infrared imaging technique - analysis of outdoor measurements
IET Digital Library Archive | 1998
|Nondestructive imaging of shallow buried objects using acoustic computed tomography
Tema Archive | 2002
|Active acoustic technique accurately locates buried PE pipe
Tema Archive | 1993
|Acoustic detection of buried landmines using pulsed ESPI
Online Contents | 2006
|