Towards the fulfillment of the Research Objectives, we performed the following activities:
Regarding RO1, we developed a novel metasurface characterization technique based on eigenvalue analysis and field averaging of the field components of its supported eigenmodes, capable of returning all electric, magnetic and magnetoelectric surface susceptibilities of a general bianisotropic metasurface. Compared with the results of other techniques in the literature, it shows very good agreement, relatively to the resonance behavior of the returned values and their position at the frequency spectrum. The advantages that distinguish the proposed technique over other related methods are its foundation on the intrinsic modal information of the eigenmodes supported by the metasurface and its independence of any wave excitation schemes or involvement of analytical polarizability calculations. The described technique was published in the article "Metasurface Characterization Based on Eigenmode Analysis and Averaging of Electromagnetic Fields", in Journal of Applied Physics, vol. 134, no. 12, 2023.
Towards the fulfillment of RO2, we initially studied the behavior of electromagnetic complementary composite periodic media via an approach based on their supported eigenmodes for in-plane wave propagation, which led to the creation of the simplified Split-Ring Resonator (SRR). As a next step, we conducted the synthesis of a new metamaterial resonant particle possessing the ability to screen the electromagnetic energy at in-plane wave incidence regardless of the wave polarization, utilizing a fully numerical approach based on the revealing of the intrinsic behavior of the utilized resonator components via the computational solution of the corresponding eigenproblems. We started with the combination of a typical EC-SRR particle with a metallic cylinder placed perpendicularly at its center, with respect to the resonator’s plane. This composite medium supports the superposition of the separate modes of its components, exhibiting simultaneous negative effective permittivity and permeability at the same axis, parallel to the cylinders. The substitution of the cylinder with the proposed simplified complementary SRR leads to the fully planar version of the polarization independent SRR (PI-SRR). Subsequently, the uniplanar version of the proposed resonator was designed, based on a combination of an ordinary one-split SRR and a complementary resonator (Fig. 1 and 2). The simulation results illustrate a very consistent behavior concerning the capability of the structures to support the electric and magnetic resonant modes almost intact, without interacting with one another, as proved by their illustrated field distributions in the proximity of the scatterers.
The synthesis of the novel Complementary SRR particle is summarized in the article "Investigation of the Electromagnetic Behavior of Complementary Split-Ring Resonators: Toward a Novel CSRR Design”, IEEE Transactions on Microwave Theory and Techniques, Early Access, (2024).
Additionally, concerning RO3, a fully numerical process for the systematic design of fully-planar antennas for 5G communications frequencies was proposed, utilizing the metamaterial-enhanced SIW as the basis platform. Two different types of fully-planar antennas were designed, for integration in 5G communications platforms, exhibiting attractive characteristics such as optimized gain and bandwidth, low cost, compactness and ease-of-fabrication: A leaky-wave fully-planar two-slot antenna and an H-plane end-fire sectoral horn antenna.
This work is summarized in the article "Systematic Synthesis of Fully-planar Antennas Based on Metamaterial-enhanced SIWs for 5G Communications”, Progress in Electromagnetic Research C, Vol. 150, pp. 105-112, 2024.
Finally, for RO4, we derived a novel field-flux Finite Element formulation for the inclusion of potentially nonreciprocal bianisotropic materials in wave propagation electromagnetic problems, introducing the required port boundary condition for the efficient excitation and absorption of the electromagnetic wave. The described work was published in "Field-Flux Finite Element Formulation for Wave Propagation in Bianisotropic Media”, 17th European Conference on Antennas and Propagation (EuCAP), Florence, Italy, 2023.
