Power deposited in biological tissues from a hand-held mobile antenna

Most countries have established the standards, based on the use of SAR (specific absorption rate) that regulate the electromagnetic emission and exposure of electronic systems. By and large, the acceptable limit of SAR for an incident plane wave is 0.08 Wlkg, averaged over the entire body. However, the question of acceptable safe level for an antenna close to the tissues, e.g., for a hand-held mobile phone, still remains open, since the standards based on the "far field" definition are no longer acceptable. Currently, many standardization groups are actively researching into this question, and they have proposed several levels of "acceptable" doses. For instance, the acceptable maximum is 2 W/kg, averaged over 10 grams and a period of 6 minutes dictated by CENELEC (ENV 50166-2), which is likely to be transformed into an European directive for compliance in the future. It is obvious, however, that extensive studies must be performed to reliably estimate the field and the SAR in the tissues before this standard could be enforced. Towards this end, France Telecom, in collaboration with the EMC laboratory of the University of Illinois, has embarked upon a project to evaluate the power deposited in the human head from a generic transceiver operating at 900 MHz. The paper presents some results based upon this study.