Computational magnetic metasurfaces in the low radiofrequency regime

This paper introduces the concept of magnetic metasurfaces able to perform computational tasks in the low radiofrequency regime by exploiting inductive coupling. Two different scenarios are conceived to demonstrate the capabilities of the proposed approach. The first one consists of a magnetic metasurface evaluating the linear combination with arbitrary coefficients of two input currents. Instead, the second example is meant to extract specific harmonics from a periodic input signal. Analytical models based on the circuital theory were firstly derived to properly design the computational core, i.e. the metasurface, for the above mentioned tasks. Then, the theoretical expectations were validated through accurate full-wave simulations and experimental measures carried out on fabricated prototypes. In terms of the manufacturing process, two different techniques were employed. Specifically, the solenoid unit cells used for the linear combination case were realized by appropriately winding single-strand copper wires, while the metasurface for harmonic extraction was implemented using PCB technology. Promising results were obtained, with root mean squared experimental errors not exceeding ideal computations by more than 18.3% in both the test cases. Notably, the proposed computational metasurfaces are characterized by easy and low-cost fabrication processes, and they can be reconfigured through digitally tunable capacitors, further enlarging the span of computational tasks achievable with the same hardware arrangement. Consequently, the developed technology constitutes a valid alternative within computational analog methodologies, opening the path to an innovative and effective way to perform complex calculations.