Influence of Phantom Shell on SAR Measurement in 3-6 GHz Frequency Range

This paper presents the results of an investigation on the effect of a thin low-dielectric material (phantom shell) on measuring the Specific Absorption Rate (SAR) in the frequency range of 3 to 6 GHz. The International Electrotechnical Commission (IEC) has started to develop a SAR measurement procedure in order to cover such frequencies. In the procedure, the SAR is measured in a liquid phantom, which is a shell filled with tissue-equivalent liquid. Although the shell is thin and has low-dielectric properties, the influence of the phantom shell is thought to increase at higher frequencies. Therefore, an investigation using the transmission line model and the Finite-Difference Time-Domain (FD-TD) method was conducted. To verify the FD-TD results, measurements were also carried out. The calculation results using the FD-TD method agree well with the measurement results. If the frequency is higher, the SAR is affected by the shell even though the shell is thinner and has much lower dielectric properties than those of the tissue-equivalent liquid. Specifically, the SAR with the shell is approximately 1.3 times higher than without the shell at 5.2 GHz for the maximum case. The deviations in the loss and the thickness for the shell do not affect the SAR more than the relative permittivity. key words: SAR, thin low-dielectric material, FD-TD method, transmission line model