An Interference-Based Quadruple-L Cross Metasurface Absorber for RF Energy Harvesting

In this letter, we propose metasurface absorbers for energy harvesting that work on the principles of destructive interference and phase cancellation. The metasurface is designed by arranging four L-shaped resonant unit cells in a fourfold symmetrical geometry leading to a cross configuration. At resonance frequency, such a geometrical configuration results in destructive interference of the electromagnetic waves emanating from diagonal elements. When used in a reflection mode as a metasurface absorber, the reciprocity theorem necessitates the flow of helicoidal resonant currents that vectorially cancel each other to make the overall metasurface nonradiative that, therefore, produces a null in the backscattering direction. A 90% absorption in simulation is achieved without explicit consideration for a free-space impedance matching or using dissipative substrate. The absorbed RF energy is harvested at 2.25 GHz to practically demonstrate the conversion efficiency of over 55% from microwave to dc.