Computational imaging with a frequency-diverse metasurface aperture

Abstract

We demonstrate image formation with radio frequency (RF) waves using a frequency-diverse metasurface antenna. The metasurface antenna consists of a planar cavity—formed from a double-layer, copper-clad printed circuit board—fed from one side by an RF source, and with a series of irises patterned into the opposite side. At any particular frequency, the cavity mode excited by the feed in turn excites the irises, each of which radiates as a magnetic dipole element. The cavity walls (fabricated using vias patterned into the circuit board) are irregular, so that the excited cavity modes exhibit considerable variation as a function of frequency. Thus, the radiated fields from the cavity-backed metasurface tend to have a series of randomly directed lobes, the number and directions of which vary significantly as a function of frequency. These radiation patterns can be used to form measurements of a scene, with the scene then estimated using computational imaging techniques. We have applied the metasurface aperture in a prototype imaging system capable of acquiring high resolution images of human-scale targets. The metasurface aperture design and reconstruction methods are general, and can be easily adapted for acoustic imaging.