Electromagnetic effects of wireless transmission for neural implants

With the extensive use of wireless devices within or at close proximity to the human body, electromagnetic effects caused by the interaction between radio frequency waves and human tissues should be considered with paramount importance. Specific absorption rate (SAR) and specific absorption (SA) have been used as key indices in measuring the electromagnetic effects on the human tissue subjected to wireless signals. This chapter focuses on the SAR, SA, and temperature variation in human tissue exposed to electromagnetic signals. International regulatory standards that govern the SAR and SA variation are explained in detail. The wireless signals are categorized according to their frequency and bandwidth, and are studied separately in the rest of the chapter. Various analytical studies on the electromagnetic effects caused by wireless signals that are present in the literature are compared in terms of the incident signal frequency, modeling methodology, and the human tissue type of interest. Two case studies that represent the electromagnetic effects for head implant applications are described in detail with graphical representations of SAR and temperature variation results. The analysis presented in this chapter shows that the electromagnetic effects caused by wireless signals depend on many factors, such as incident frequency, signal bandwidth, tissue properties, antenna properties, and positioning of the wireless device.