Christ A, Samaras T, Klingenböck A, Kuster N
Foundation for Research on Information Technologies in Society, IT'IS, Zeughausstr 43, 8004 Zürich, Switzerland.
Phys Med Biol. 2006 Oct 7;51(19):4951-65. doi: 10.1088/0031-9155/51/19/014. Epub 2006 Sep 18.
Currently, standards for the compliance testing of wireless devices are being extended to cover a wider frequency band and different usage patterns of mobile phones as well as of novel body-worn and handheld devices. As a consequence, not only the head but also strongly varying tissue distributions of the body are exposed to electromagnetic radiation. Several authors have reported changes in the SAR absorption of body tissue due to the presence of a low permittivity fat layer. This paper identifies two different effects which can lead to increased SAR in layered tissue in comparison to the SAR assessed using homogeneous tissue simulating liquid: (1) for larger distances between the tissue and the antenna, standing wave effects occur depending on the frequency and fat layer thickness. (2) In the very close near-field (distances approximately lambda/40), reactive E-field components lead to high local absorption in the skin. The latter effect occurs at lower frequencies and depends on the antenna type. Modification of the parameters of the homogeneous liquids cannot compensate for these effects. However, a conservative exposure estimate can be obtained by applying a multiplication factor between 1 and 3 to the values assessed using current experimental dosimetric techniques.
目前，无线设备的合规测试标准正在扩展，以覆盖更宽的频段以及手机、新型可穿戴设备和手持设备的不同使用模式。因此，不仅头部，而且身体中变化很大的组织分布也会受到电磁辐射。几位作者报告了由于低介电常数脂肪层的存在而导致身体组织比吸收率（SAR）吸收发生变化。本文确定了两种不同的效应，与使用均匀组织模拟液评估的SAR相比，这两种效应会导致分层组织中的SAR增加：（1）对于组织与天线之间的距离较大时，根据频率和脂肪层厚度会出现驻波效应。（2）在非常近的近场（距离约为λ/40）中，感应电场分量会导致皮肤中的局部高吸收。后一种效应在较低频率下出现，并取决于天线类型。均匀液体参数的修改无法补偿这些效应。然而，通过对使用当前实验剂量技术评估的值应用1到3之间的乘法因子，可以获得保守的暴露估计值。
