Matter's Electromagnetic Signature Reproduction by Graded-Dielectric Multilayer Assembly

A lot of effort has been devoted in the last decades by technology research to realizing materials with a priori defined electromagnetic (EM) properties. One of the challenges at present is to configure the reflection coefficient (RC) of a structure so that any shape of a fixed microwave response is followed. A method for realizing microwave absorbers made by carbon nanocomposite layers assembly able to mimic a given reflection profile is described and experimentally validated. The multilayer design (layer sequence, material, and thickness) is pursued by means of a customized numerical optimization algorithm, which allows to get the required microwave behavior. The novelty of the research is the possibility of tuning the EM field propagation through the combination of different materials in a specific layered compound, in order to imitate the response of any "real" object (i.e., with known EM properties). For the experimental validation of the process, three multilayered structures were designed and manufactured, and their microwave RC was measured in the frequency range of 2-18 GHz. The comparison with the related targets (an ideal frequency selective pattern and the defined profiles of dry soil and salt water as retrieved from literature survey) highlights the effective simulating capability of the realized structures. The preliminary results suggest to exploit the graded-dielectric properties provided by carbon-based nanocomposites for EM mimicking purposes: this would be an ideal approach to tackle still unsolved issues in EM compatibility, remote sensing, communication, and safety fields, as well as for low-cost and time-saving metrology applications.