Specific absorption rates in the human head and shoulder for passive UHF RFID systems

In this paper, we use a human head and shoulder model to extend the theory and analysis of specific absorption rates (SAR) in the human head due to radiation caused by passive radio frequency identification (RFID) reader systems. We use a finite-element method (FEM), and a human head and shoulder model with a voxel size of 8mm for the tetrahedral to analyze the peak one-voxel SAR, spatial-peak 1g cube of tissue SAR, spatial-peak 10g cube of tissue SAR, and the average SAR in the human head. We present analytical evaluations to study the SAR in the human head at 1W radiated power output of a 7.4dB gain RFID reader patch antenna at distances of 10cm, 100cm and 1000cm from the front of the human head, at the cut-plane intersection of the human eye. We also show that in an ideal absorption environment, an RFID reader at 10cm from the human head presents a SAR above 1.6W/kg for both the spatial-peak 1g and 10g cube of tissue, the maximum value allowed by the Federal Communications Commission (FCC) in the US.