Millimeter Wave and Terahertz Synthetic Aperture Radar for Locating Metallic Scatterers Embedded in Scattering Media

A rail-mounted synthetic aperture radar has been constructed to operate at W-band (75-110 GHz) and a terahertz (THz) band (325-500 GHz) in order to ascertain its ability to detect and locate isolated small, visually obscured metallic scatterers embedded in highly scattering dielectric hosts that are either semitransparent or opaque. A 'top view' two-dimensional (2-D) algorithm was used to reconstruct scenes from the acquired data, locating metallic scatterers at W-band with high-range and cross-range resolution of 4.3 and 16 mm, respectively, improved to 0.86 and 5 mm at the THz band. Millimeter-sized metallic scatterers were easily located when embedded in semitransparent, highly scattering target hosts of polystyrene and polyethylene packing foam but were more difficult to locate when embedded in relatively opaque, highly scattering polyisocyanurate insulation panels. Although the THz band provided the expected greater spatial resolution, it required the target to be moved closer to the rail and had a more limited field of view that prevented some targets from being identified. Techniques for improving the signal-to-noise ratio are discussed. This paper establishes a path for developing techniques to render a complete 3-D reconstruction of a scene rapidly.