Selective Microwave Wireless Power Transfer to Sensors Embeddedin Concrete at Sub-wavelength Spacing using ElectromagneticTime-reversal Technique

Wireless power transfer has become a trending research area for remotely transferring power. This paper presents the numerical simulation study of selective wireless power transfer to closely spaced wireless sensors embedded in reinforced concrete. A selective microwave wireless power transfer is achieved at a 10 mm separation between tightly-coupled monopole antennas (wireless sensor antennas). Both tightly-coupled wireless sensors operate at 2.45 GHz, hence beating the diffraction limit at λ/12 with the incorporation of additional scatterers in the reinforced concrete environment. The main objective is to realize selective wireless power transfer to wireless sensors with subwavelength separation (closely spaced) to which one makes the power request. Here, the presence of meta-structures creates some randomness serving as scatterers in the use of the electromagnetic time-reversal technique which enhances the spatial refocusing beyond the diffraction limit. This implies that the focal spot is less than half of the carrier wavelength at the operating frequency. At any time that one of the tightly-coupled sensor antennas sends a power request, power will be transferred to it alone. Cases of dry concrete with and without reinforced bars have been studied with electromagnetic time-reversal techniques for the closely spaced sensors embedded in concrete.