Consideration of current mobile communication antenne technology when determining exposure to HF-EMF

What is the issue?

Modern mobile communications networks use antennas that can change their radiation characteristics electronically and adapt them as needed. The process is known as lobe forming or beam forming of radar systems. However, its use in mobile communication technology is still comparatively young. The technology is used mainly for base stations that operate at frequencies of a few gigahertz and are thus compatible with the fifth-generation mobile communications standard.

What is the current situation?

High-frequency measurement technology is highly developed. In principle, suitable measurement methods are available for the entire frequency range used by mobile communications. However, the determination of emission contributions from base station antennas with the described characteristics poses a metrological challenge. On one hand, rapidly changing field distributions must be correctly recorded and evaluated. On the other hand, a strategy for determining the maximum contribution of a transmitter to exposure based on a current measurement result must be developed. Previous methods, in which the signal sections emitted by a system are measured consistently and used as a starting point for the assessment, have reached their limits.

What are the objectives of the BfS research project?

In the project, measurement strategies with which actual, typical, and maximum possible emission are to be developed so that exposure contributions from mobile communications base stations with beam forming antennas can be reliably determined. The emission and exposure contributions are to be determined at 100 selected locations in the near and far vicinity of base station sites equipped with the antenna technology.

What were the results of the research project?

The measurements were carried out in the vicinity of 5G base stations operating in the 3.6 GHz frequency band. The maximum possible immission contributions reached 0.2 % to 28.6 % of the field strength limits specified for this frequency band in the 26th Ordinance on the Implementation of the Federal Immission Control Act (61 V/m, 0.16 A/m). The contributions thus covered a range of 43 dB; the median was 4.7 %. The actual immission contributions were significantly lower at the time of the measurements. The results report contains a description of the measurement strategies developed and a documentation of the measured values.