Frequency-diverse aperture imaging using an open cavity with a rough base

Abstract

This paper proposes a single-shot computational imaging using a new frequency-diverse aperture, an open-ended cavity with a rough surface base. First, it shows that scattering from a conducting rough surface made of conducting cones placed at random positions on a conducting ground plane, normally illuminated by an ultra-wideband horn antenna (working in the 2–20 GHz range) provides random patterns with a frequency correlation function (FCF) width of Δf, about hundreds of MHz. Next, by introducing four conducting walls placed around the rough surface, it obtains a higher number of spatially uncorrelated radiation patterns and a narrower FCF width of about Δf/10, tens of MHz. To approximate the radiation patterns and measurement matrices in the numerical simulations, the geometrical optics (GO) approximation is used taking into account multiple interactions. On the other hand, to estimate them in practice, a trihedral corner reflector installed on an XYZ positioning table is employed. Finally, the image of a planar object with the shape of plus is reconstructed using the minimum least-squares technique. The paper shows that for a 0.81 square metre image size, a decent-focused image with a pixel size of about 0.81/400 square metres (about 5 cm × 5 cm) is realisable by using 400 frequency samples within the frequency range of 2–20 GHz.