Radio frequency electromagnetic field compliance assessment of multi‐band and MIMO equipped radio base stations

Abstract

In this paper, different methods for practical numerical radio frequency (RF) exposure compliance assessments of radio base station (RBS) products are investigated. Both multi-band base station antennas and antennas designed for multiple-input multiple-output (MIMO) transmission schemes are considered. For the multi-band case, various standardized assessment methods are evaluated in terms of resulting compliance distance with respect to the International Commission on Non-Ionizing Radiation Protection (ICNIRP) reference levels and basic restrictions. Both single frequency and multiple frequency (cumulative) compliance distances are determined, using numerical simulations for a mobile communication base station antenna transmitting in four frequency bands between 800 MHz and 2600 MHz. The assessments are conducted in terms of the root-mean squared electromagnetic field, the whole-body averaged SAR and the peak 10g averaged SAR. In general, assessments based on peak field strengths are 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. As long as adult exposure is considered, the results also indicate that even shorter compliance distances are obtained by using assessments based on localized and wholebody SAR. Numerical simulations, using base station products employing multiple-input multipleoutput (MIMO) transmission schemes, are performed as well and are in good agreement with reference measurements. The applicability of various field combination methods for correlated exposure is investigated, and best estimate methods are proposed. It is also shown, that field combining methods generally considered as conservative may be used to efficiently assess compliance boundary dimensions of single-and dual-polarized multicolumn base station antennas with only minor increases in compliance distances. Key words: Mobile communication; Electromagnetic field exposure; EMF compliance; SpecificAbsorption Rate; MIMO; Multi-standard radio base station; Multi-band radio base station. INTRODUCTIONBefore radio base station (RBS) products are placed on the market, their manufacturers conduct electromagnetic field (EMF) product compliance assessments to make sure that the equipment fulfills relevant regulatory requirements on EMF exposure. The purpose of these assessments is to determine compliance boundaries outside of which the radiofrequency (RF) EMF exposure is below applicable exposure limits. The most widely adopted exposure limits are specified by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) [ICNIRP, 1998]. For frequencies between 10 MHz to 10 GHz, including the frequency range used for mobile communications, the fundamental dosimetric quantity is the specific absorption rate (SAR). SAR corresponds to the rate of dissipated energy per unit mass within the exposed body due to the incident electromagnetic fields. Assessing exposure with respect to the basic re...

Statistical Approach for Human Electromagnetic Exposure Assessment in Future Wireless Atto-Cell Networks

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Recent Trend in Electromagnetic Radiation and Compliance Assessments for 5G Communication

“…In RF EMF assessments for large array multiport antennas, the combined exposure from all ports needs to be considered. Hence, different assessment methods for antenna array intended for beamforming applications have been investigated in [25][26][27][28][29]. The author in [25] shows that accurate and efficient EMF compliance assessments can be conducted by using embedded element approach.…”

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Radiofrequency exposure near an attocell as part of an ultra‐high density access network

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