Is the radio wave of the 5G mobile terminal safe?Mechanism of NICT technology to be evaluated | New Switch by Nikkan Kogyo Shimbun

With the launch of 5th generation communication (5G) mobile phone services, some public interest in the safety of the invisible radio waves has become very high. In Japan, radio wave protection guidelines have been established to ensure the safety of radio waves, and conformity evaluation of mobile phone terminals, etc. is obligatory according to these guideline values.

In this way, the technology for evaluating conformity with radio wave protection guidelines is a very important technology that is indispensable for the safe and secure life of the public. In the frequency band (6 gigahertz or less) mainly used in 4G and 5G mobile phone terminals that we usually use, the specific absorption rate (power absorption per unit mass of living tissue) is based on the compatibility evaluation method. The amount, SAR = Specific Absorption Rate) is measured, and the conformity to the guideline value indicated by the specific absorption rate is confirmed.

The National Institute of Information and Communications Technology (NICT) is working on the development and improvement of measurement technology and the reliability evaluation of the technology itself regarding the conformity evaluation technology of mobile phone terminals to the radio wave protection guidelines. Among these, the examination of the calibration method of the SAR probe used for SAR measurement is one of the important factors. In the existing SAR probe calibration method, as shown on the left side of the figure, the standard electric field generated in the waveguide filled with the bioequivalent liquid agent is measured by the SAR probe. This is done using a waveguide of the appropriate size for each frequency you want to calibrate.

5G mobile phone terminals use higher frequencies than earlier mobile phone terminals, but the size of the waveguide decreases as the frequency increases, so the SAR probe is too large for the waveguide. As a result, the electric field in the waveguide is disturbed and proper calibration cannot be performed.

To solve this problem, an antenna that plays the same role as the waveguide of the existing method is placed in a water tank that is much larger than the waveguide as shown on the right of the figure, and the standard electric field generated from it (exactly). We are developing a new method to measure and calibrate the electric field strength that can be calculated from the measurable antenna input power with a SAR probe.

Since this method can handle high frequencies and the frequency of antenna replacement for each frequency is low, simplification of the calibration system can be expected. We would like to contribute to a safe and secure life through the development of radio wave safety evaluation technology.

Nikkan Kogyo Shimbun January 18, 2022