An Interferometric Synthetic Aperture Radar (InSAR) system to map the bedrock topography underneath the sand in deserts and arid areas is presented. It is anticipated to greatly increase the efficiency of oil field and ground water exploration as well as environmental and archaeological studies. The proposed system consists of two InSAR subsystems, one operating at Ka-band to map the sand topography and the other operates in the VHF band to map the subsurface topography. It is shown that conventional InSAR processing produces unacceptable error in height estimation since it does not account for the refraction and the different propagation velocity in the sand. Thus, a new inversion algorithm is developed which can be used to accurately estimate the bedrock topography for arbitrary sand and bedrock geometries. The inversion algorithm is verified experimentally using a scaled model in the lab. One of the main concerns was the use of conventional SAR focusing techniques for imaging the subsurface region. This can result in significant image degradation and lower limit on the minimum achievable azimuth resolution. Thus, a new subsurface iterative focusing technique is developed to address these challenges. One of the main practical system implementation issues is the antenna design for the VHF system since very wideband and very compact antennas are desired. Thus a number of compact and low profile Ultra-Wideband antennas are also developed. These antennas have sub-wavelength sizes and most of them have bandwidths exceeding one octave. It is shown that these antennas cannot only be used in our system, but because of their performance and size they are also suitable for use in many other applications such as see through wall radars and UWB communication systems.
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