Effect of dielectric properties on the peak 1-and 10-g SAR for 802.11 a/b/g frequencies 2.45 and 5.15 to 5.85 GHz

Compliance with 1- or 10-g specific absorption rate (SAR) safety guidelines is required in various countries for all newly-introduced personal wireless devices such as Wi-Fi PCs. Even though the dielectric properties of the human tissues are known to be nonuniform and highly variable, relatively rigid adherence to prescribed dielectric properties (ε_r,σ) is required for compliance testing of such devices. Using some typical near-field radiators, we have examined the effect of dielectric properties for SAR measurement fluids with conductivities varying by 2:1 to show that both 1- and 10-g SARs vary by less than ±2%-4% for the 802.11a band 5.15 to 5.825 GHz and only slightly more at the lower 802.11 b/g frequency of 2.45 GHz. This is due to higher surface SAR but shallower depth of penetration of EM fields for the higher conductivity media resulting in nearly identical SARs for cubical volumes associated with 1- or 10-g of tissue, respectively. Also studied, is the effect of lower ε_r fluids recommended in some standards which results in slightly higher and, thus, a conservative assessment of SAR.