Thors Björn, Thielens Arno, Fridén Jonas, Colombi Davide, Törnevik Christer, Vermeeren Günter, Martens Luc, Joseph Wout
Ericsson Research, Stockholm, Sweden.
Bioelectromagnetics. 2014 May;35(4):296-308. doi: 10.1002/bem.21843. Epub 2014 Feb 13.
In this paper, different methods for practical numerical radio frequency exposure compliance assessments of radio base station products were investigated. Both multi-band base station antennas and antennas designed for multiple input multiple output (MIMO) transmission schemes were considered. For the multi-band case, various standardized assessment methods were evaluated in terms of resulting compliance distance with respect to the reference levels and basic restrictions of the International Commission on Non-Ionizing Radiation Protection. Both single frequency and multiple frequency (cumulative) compliance distances were determined using numerical simulations for a mobile communication base station antenna transmitting in four frequency bands between 800 and 2600 MHz. The assessments were conducted in terms of root-mean-squared electromagnetic fields, whole-body averaged specific absorption rate (SAR) and peak 10 g averaged SAR. In general, assessments based on peak field strengths were found to be less computationally intensive, but lead to larger compliance distances than spatial averaging of electromagnetic fields used in combination with localized SAR assessments. For adult exposure, the results indicated that even shorter compliance distances were obtained by using assessments based on localized and whole-body SAR. Numerical simulations, using base station products employing MIMO transmission schemes, were performed as well and were in agreement with reference measurements. The applicability of various field combination methods for correlated exposure was investigated, and best estimate methods were proposed. Our results showed that field combining methods generally considered as conservative could be used to efficiently assess compliance boundary dimensions of single- and dual-polarized multicolumn base station antennas with only minor increases in compliance distances.
本文研究了无线电基站产品实际数值射频暴露合规性评估的不同方法。研究对象包括多频段基站天线和为多输入多输出（MIMO）传输方案设计的天线。对于多频段情况，根据相对于国际非电离辐射防护委员会的参考水平和基本限制得出的合规距离，对各种标准化评估方法进行了评估。使用数值模拟确定了在800至2600 MHz四个频段内发射的移动通信基站天线的单频和多频（累积）合规距离。评估是根据均方根电磁场、全身平均比吸收率（SAR）和峰值10 g平均SAR进行的。一般来说，基于峰值场强的评估计算量较小，但与结合局部SAR评估使用的电磁场空间平均相比，会导致更大的合规距离。对于成人暴露，结果表明，使用基于局部和全身SAR的评估可获得更短的合规距离。还对采用MIMO传输方案的基站产品进行了数值模拟，结果与参考测量结果一致。研究了各种场组合方法在相关暴露中的适用性，并提出了最佳估计方法。我们的结果表明，通常被认为保守的场组合方法可用于有效评估单极化和双极化多列基站天线的合规边界尺寸，且合规距离仅略有增加。
