Subsurface radar (SR) techniques are used in situations where the scan area consists of a material that has different dielectric properties to the one where the radar elements are located. For many SR applications, the targets are at a shorter distance than in airborne/seaborne radar scenarios. Additionally, the data acquisition process may be performed along nonconventional scan trajectories in order to suit the geometry of the scan area. This paper presents a novel reconstruction technique for SR data collected along circular and semi-elliptical scan trajectories. The spectrum of the collected data is processed in order to locate the spatial origin of the reflections and remove the artifacts introduced by the scan trajectory. Sampling constraints and the behavior of the point-spread function (PSF) in both scan geometries are discussed and illustrated. The proposed algorithm was tested using simulated examples and experimental data collected from phantoms that mimic the dielectric properties of two novel SR applications: breast cancer detection and wood inspection. The proposed method yielded promising results in terms of both spatial accuracy and focal quality.
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