SAR Analysis in Dispersive Tissues for In Vivo UWB Body Area Networks

In this paper, we present the impact on specific absorption ratio (SAR) distribution by dispersive media in wireless body area networks (BAN). For BAN systems, ultrawideband (UWB) transmissions have received much attention because of its low power spectrum and its small antenna size. When we adopt the UWB technique to BAN systems, the SAR analysis is highly demanded for predicting the exposure level prior to experiments and products. It is well-known that the dielectric properties of human tissues have a great spectrum dependency, that renders a difficulty of an SAR analysis by electromagnetic field simulations through the finite-difference time-domain (FDTD) methods for wideband signals. For frequency-dependent analysis, the piecewise linear recursive convolution (PLRC) method is useful for dealing with the dispersive media. To employ the PLRC method, we re-formulate the dielectric spectrum properties of human organs approximating the so-called 4-Cole-Cole model. We reveal that we need to consider the dispersive effect of human tissues to analyze the SAR according to the UWB bandwidth.