A Hologram Reconstruction Algorithm for Landmine Recognition and Classification Based on Microwave Holographic Radar Data

We have developed a stand-off holographic subsurface radar (HSR)operating at 2 GHz with amplitude and phase outputs for detection and classification of buried shallow objects, including plastic landmines. The microwave holograms obtained in this way contain information about the size and shape of the buried objects within the penetration depth. The reconstruction of the electromagnetic field on a plane parallel to the scanning plane has been repeatedly addressed in the literature; however, the propagation of the incident field through the air-soil interface generates a refracted path into air and soil with a different velocity and thus results in different phase changes. Furthermore, the actual dimensions of the antenna aperture in relation to the scanning surface and the real radiation pattern are to be considered. In this work, we define and test an algorithm that uses the amplitude and phase data derived from the use of a finite-sized monostatic antenna. The antenna, with an aperture comparable to the buried object size (circular aperture of 11.5 cm of diameter), is positioned at few centimetres from the ground, and scans an area containing the buried object to provide the basic hologram. We have investigated the proposed method to assess the improvement in the detection of buried objects.