Abstract
Microwave imaging (MWI) systems are usually enclosed within casings,
e.g., in order to contain the utilized coupling liquid or to help mount
the antenna system. On the other hand, inverse scattering algorithms,
which are used to process the measured microwave scattering data, often
assume that the background medium of the imaging system extends to
infinity (i.e., unbounded background medium assumption). Thus, they do
not consider the reflections occurring at the system enclosure. For such
algorithms to yield successful images, these reflections need to be
minimized, e.g., via the use of a lossy coupling liquid. As an
alternative to a lossy background medium which also reduces the desired
signal level, this paper investigates the use of metallic-backed
absorbing metasurfaces as the MWI system enclosure in order to (i)
reduce these reflections, and also (ii) to shield the MWI system from
external interference. Using simulated data, we then show that standard
inverse scattering algorithms, employing the free-space assumption, can
successfully process the data collected under the metasurface enclosure
and yield acceptable permittivity images. The advantages and
disadvantages of absorbing metasurface enclosure, along with the
limitations of this study, will also be discussed. Finally, an absorbing
metasurface is fabricated and its reflectivity is experimentally
evaluated.