On the Use of Absorbing Metasurfaces in Microwave Imaging

Ziqi Liu,Nozhan Bayat,Puyan Mojabi

doi:10.1109/tap.2021.3098588

Ziqi Liu, Nozhan Bayat + Show 1 more

Open Access

https://doi.org/10.1109/tap.2021.3098588

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Abstract

Microwave imaging (MWI) systems are usually enclosed within casings in order to contain the utilized coupling liquid or help mount the antenna system. On the other hand, inverse scattering algorithms often assume that the background medium of the imaging system extends to infinity (i.e., unbounded background medium assumption). Thus, they typically 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 communication investigates the use of metallic-backed absorbing metasurfaces as the MWI system enclosure in order to 1) reduce these reflections and also 2) 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.

Highlights

M ICROWAVE imaging (MWI) is a non-invasive and nonionizing imaging modality that creates qualitative or quantitative images of the relative complex permittivity profile of an object of interest (OI) [1]–[5]
The inverse scattering approach to MWI, which is the focus of this paper, is usually concerned with reconstructing a quantitative image of the OI’s relative complex permittivity profile
We consider three synthetic targets to demonstrate the performance of the absorbing metasurface enclosures

Summary

Introduction

M ICROWAVE imaging (MWI) is a non-invasive and nonionizing imaging modality that creates qualitative or quantitative images of the relative complex permittivity profile of an object of interest (OI) [1]–[5]. The inverse scattering approach to MWI, which is the focus of this paper, is usually concerned with reconstructing a quantitative image of the OI’s relative complex permittivity profile In this approach, the OI is often irradiated from different angles, and the resulting scattered fields are collected at different locations around the OI. The inverse scattering approach employs a nonlinear optimization scheme to iteratively reconstruct a quantitative relative complex permittivity profile by minimizing the discrepancy between the simulated scattering data from a predicted permittivity image and the measured scattered data from the true This paragraph of the first footnote will contain the date on which you submitted your paper for review. The financial support of the Natural Sciences and Engineering Research Council (NSERC) of Canada, University of Manitoba’s UMGF and GETS Program, as well as the Canada Research Chair (CRC) Program is acknowledged

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