Metasurface Characterization for Low Frequency Shielding Purposes

The purpose of the present study is to ensure that a metasurface, consisting of a 5×5 array of resonating coils at different frequencies, owns shielding properties in the frequency range adopted by Wireless Power Transfer (WPT) systems for automotive applications, i.e. kHz frequency range. The dimensions of the slab and the individual unit cell tailored for the system have been chosen to completely cover a pre-existing small-scale WPT system at low frequencies, since a WPT system had been previously developed by the authors in an earlier study. The unit cell of the array is made up of a solenoid featuring M = 30 turns, crafted from enamel-coated copper wire with a gauge of AWG28 (equivalent to a wire diameter of 0.315mm). The solenoid has a diameter (D) of 4 cm and a height (h) of 11.05mm. The metasurface has a total surface equal to 20 cm x 20 cm. (M. Simonazzi, L. Sandrolini, S. Barmada, and N. Fontana, “Optimal Metamaterial Configuration for Magnetic Field Shielding in Wireless Power Transfer Systems,” 2023 IEEE Wireless Power Technology Conference and Expo (WPTCE), San Diego, CA, USA, 2023, pp. 1–5, doi: 10.1109/WPTCE56855.2023.10216186). A numerical FEKO model has been implemented and simulated with this purpose. The results in terms of Shielding Effectiveness (SE) within the interested frequency range have demonstrated that the metasurface behaves as a shield around 105kHz: the last properties can be obtained by exploiting the symmetry of the system and by tuning each unitcell at 6 different frequencies in the interested frequency range, with 6 different capacitors obtained by an optimization performed at steady-state regime. The SE has been evaluated with two simulations: one in which two simple non resonating coils are fed in unloaded conditions of use and one in which the metasurface has been inserted between the coils (Fig. 1 (left)). In both cases the scattering parameter S21 has been evaluated. The shielding effectiveness in logarithmic scale has been determined, as in Eq. (1) and shown in Fig. 1 (right). At the conference, an early-stage prototype of the metasurface will be presented and further details about its electrical properties will be provided by the use of measurements.