Reduction of specific absorption rate in human tissues using split ring resonators

In this paper, we are presenting a framework for investigation on mobile phone and human head interaction. As we all know that some of the radio waves emitted by a mobile phone handset are absorbed by the human head. The rate at which radiation is absorbed by the human body is measured by the Specific Absorption Rate (SAR). The SAR is calculated by using Finite Difference Time Domain (FDTD) Method. The results of the calculated peak or average SAR are correlated with the distance between the antenna and phantom and with the standing wave ratio at the antenna feed point. The results show that the energy absorbed by the biological tissue primarily depends on the operational parameters of the handset's antenna. To reduce the SAR, we use metamaterials to reduce the electromagnetic interaction between the mobile phone antenna and human head. It is found that the SAR in the head can be reduced by placing the metamaterials between the antenna and the head. By arranging split ring resonators (SRRs) periodically we get an electromagnetic shield. By properly designing structural parameters of SRRs, the effective permeability of the medium can be made negative around 900 and 1800 MHz GSM frequency bands. The design procedure will be described. Numerical results of the SAR values in a muscle cube and brain with the presence of SRR's exhibit significant SAR reduction. These results can provide helpful information in designing the mobile communication equipments for safety compliance.