A UHF Near-Field Link for Passive Sensing in Industrial Wireless Power Transfer Systems

This paper presents an innovative nonconventional exploitation of a self-resonant capacitive near-field link at UHF, for data communication, to be combined in a compact wireless power transfer (WPT) system. At UHF, an increased channel transfer efficiency is made possible by exploiting two faced auto-resonant structures, such as split-ring resonators (SRRs), one at each far-end side of the link. Their physical layouts are designed to ensure accurate prediction of both the resonant frequency and the resulting frequency-variable behavior of the two-port arrangement. This network is then used in a passive sensing system, based on a smart exploitation of the dc-power dc-load relationship of a standard RF identification (RFID) rectifier, to convert the data of a remote sensor, representing the system variable load. The reflected power variations at the transmitter side, due to the dc load variations, are successfully used to perform the sensor readout. The entire sensing system is first optimized by means of nonlinear circuit and electromagnetic (EM) simulations. Experimental data, compared to prior results, demonstrate the strength of the adopted approach.