Biomedical concerns in wireless communications.

The last decade witnessed rapid development of new communication technologies and their broad acceptance at large. Digital wireless telephones are the most popular example of these technologies. There are two aspects of these technologies that are related to human health and therefore biomedical engineering. First, antennas of some devices are in close proximity to the user's head, thus possibly producing locally excessive energy deposition. Second, radiofrequency (RF) signals emitted are amplitude modulated at extremely low frequencies, potentially eliciting different biological effects from those of unmodulated RF radiation. Recent progress in addressing these two issues is reviewed in this article. Another area of research and concern not covered here is electromagnetic interference (EMI) with medical devices. Considerable research has been conducted on the development of a new method for numerical and experimental evaluation of the spatial distribution of the power deposition in tissue. Improved implantable electric field probes and automated scanning systems are presently available. With respect to numerical evaluation of electric fields in tissue, the finite difference time domain (FDTD) technique has proven to be a useful and accurate tool. These developments also are critical in view of the regulatory requirements now imposed on mobile/portable transmitters. Similarly, significant research effort on biological effects of modulated fields has been undertaken. Most of the studies are still in progress, and further research agendas have been proposed.