Active Self-Tuning Metasurface With Enhanced Absorbing Frequency Range for Suppression of High-Power Surface Currents

We demonstrate a unique metamaterial surface that actively tunes its resonance frequency to match the frequency of incident electromagnetic waves, providing a broadband self-tuning absorber. The metasurface is constructed with nonlinear circuit components and is capable of detecting the incoming signals and adapting its resonant frequency without any external control. The fabricated prototype achieves 70% of -3 dB fractional frequency range compared with the intrinsic limit of around 5% for a passive absorbing surface of the same thickness. Its performance is experimentally verified by measuring absorption as a function of frequency with the self-tuning circuits turned on or off to demonstrate the self-tuning capability and the increase in the absorption frequency range. The measurements were performed for both TM and TE polarizations and various oblique incident angles. The proposed metasurface has a threshold power level for the absorption of incident waves and only absorbs high-power interfering signals while allowing small signals, such as for communications.