Advancing electromagnetic inversion for characterization and design

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This research program is concerned with Electromagnetic (EM) inversion, which is defined as the process by which some properties of a region of interest are inferred from its external EM signatures. This process involves solving EM inverse problems, which are often cast as optimization problems. The unique aspect of this research program is that all its algorithms and techniques stem from the consistent framework of EM inversion, and are then applied to impact diverging application areas: near-field microwave imaging, microwave sea ice remote sensing, antenna characterization, and design of EM engineered surfaces.******In this research program, the external EM signatures to be used by inversion algorithms are either measured EM data (e.g., EM fields, radar cross section) or desired EM properties to be realized. On the other hand, the properties to be inferred are either (i) dielectric properties of objects or regions that scatter incident EM waves (e.g., biological tissues or sea ice), or (ii) equivalent currents of EM sources that generate EM waves (e.g., antennas). ******The EM inversion framework is often used for imaging, remote sensing, and non-destructive evaluation applications, which we collectively refer to as characterization applications. This research program not only advances the topic of EM inversion for characterization, but also investigates EM inversion for design applications.******Within the area of EM inversion for characterization, our main focus is (I) to develop novel algorithms and techniques to enhance the achievable accuracy, spatial resolution, and detection capabilities, and (II) to develop more affordable inversion strategies by utilizing magnitude-only EM data. This will be pursued to advance three application areas: microwave biomedical imaging, microwave remote sensing of oil spills in sea ice, and phaseless antenna measurements.******Within the area of EM inversion for design, the key challenge to be addressed is how to use the inversion framework to facilitate the macroscopic design of EM metasurfaces, which are engineered surfaces composed of subwavelength elements. These surfaces are important as they provide a systematic means to transform a given EM field to a desired one by imposing appropriate boundary conditions. This, therefore, will advance the application area of antenna engineering.******The long-term objective of this research is to advance the topic of EM inverse problems so that (1) inversion results with maximum quantitative accuracy and spatial resolution can be systematically achieved for characterization applications and (2) EM inversion is established as an effective complementary framework to facilitate the design of complex EM systems. This research program will train highly qualified personnel (HQP) with hardware and software skills. These HQP can then use their expertise in EM inversion to impact various EM characterization and design applications.**