Forward Looking GPR Sidelobe Reduction Using L1-norm Minimization

Ground Penetrating Radar (GPR) has been applied for several years to the problem of detecting both anti-personnel and anti-tank landmines. One area of research is using Forward Looking GPR (FLGPR) to detect mines. While FLGPR has the advantage of standoff versus downward looking GPR, the responses from buried targets generally decrease while the responses from clutter increase. One source of clutter is from sidelobes and grating lobes caused by off-road clutter. As it is not possible to get a narrow beamwidth at the low frequencies required to get ground penetration, FLGPR receives responses from both on and off the road. Off-road clutter responses are often much stronger than the responses from buried mines. These off-road clutter objects can produce sidelobes that overlap with and obscure the responses from inroad targets. This becomes especially problematic if the antenna array spacing is not fine enough and grating lobes are formed. To reduce both the sidelobes and grating lobes, a technique using L1-norm minimization was tested. One advantage of this technique is it only requires a single aperture. The resulting image retains phase information which allows the images to be then coherently summed, resulting in better quality images. In this paper a description of the algorithm is provided. The algorithm was applied to a FLGPR data set to show its ability to reduce both sidelobes and grating lobes. Resulting images are shown.