Multi-frequency synthetic-aperture imaging with a lightweight ground penetrating radar system

The detection of buried objects, particularly hazardous waste containers an d unexploded ordnance (UXO), has gained significant interest in the Unites States in the late 1990s. The desire to remediate the thousands of sites wo rldwide has become an increasing concern and the application of radar to th is problem has received renewed attention. The US Department of Energy's Sp ecial Technologies Laboratory (STL), operated by Bechtel Nevada, has develo ped several frequency-modulated, continuous-wave (FM-CW) ground penetrating radar (GPR) units. To meet technical requirements for higher-resolution da ta, STL and the University of California, Santa Barbara (UCSB) is investiga ting advanced GPR hardware, signal processing, and synthetic-aperture imagi ng with the development of an innovative system. The goal is to design and fabricate a lightweight, battery-operated unit that does not require surfac e contact, can be operated by a novice user, and can achieve improved resol ution. The latter is accomplished by using synthetic-aperture imaging, whic h forms the subsurface images by fully utilizing the data sequences collect ively along a scan path. We also present the backward propagation algorithm as the basic structure of the multiple-frequency tomographic imaging techn ique, and the conventional fast Fourier transform (FFT) method which can be described as a degenerated case of the model where the computation procedu re is approximated under the narrow-beam assumption. (C) 2000 Elsevier Scie nce B.V. All rights reserved.