Design and Implementation of a Specialised Millimetre-Wave Exposure System for Investigating the Radiation Effects of 5G and Future Technologies

Abstract

As the fifth-generation (5G) network is introduced in the millimetre-wave (mmWave) spectrum, and the widespread deployment of 5G standalone (SA) is approaching, it becomes essential to establish scientifically grounded exposure limits in the mmWave frequency band. To achieve this, conducting experiments at specific frequencies is crucial for obtaining reliable evidence of potential biological impacts. However, there is a literature gap where experimental research either does not utilise the mmWave high band (e.g., the 26 Gigahertz (GHz) band) or most studies mainly rely on computational approaches. Moreover, some experimental studies do not establish reproducible test environment and exposure systems. Addressing these gaps is vital for a comprehensive exploration of the biological implications associated with mmWave exposure. This study was designed to develop and implement a mmWave exposure system operating at 26 GHz. The step-by-step design and development of the system are explained. This specialised system was designed and implemented within an anechoic chamber to minimise external electromagnetic (EM) interference, creating a controlled and reproducible environment for experiments involving high-frequency EM fields. The exposure system features a 1 cm radiation spot size, enabling highly localised exposure for various biological studies. This configuration facilitates numerous dosimetry studies related to mmWave frequencies.

Keywords: 5G; RF exposure system; mmWave; non-ionising radiation; radiation protection.

Figure 1

(A) The operational mmWave exposure system; (B) schematic diagram illustrating the exposure system and its components.

Figure 2

(A) Schematic representation of the antenna holder, illustrating its shape and dimensions. (B) The antenna holder with the antenna in position and the sample holder being adjusted at a distance of 133 mm from the antenna to capture the focal spot.

Figure 3

Anechoic chamber facility at the 6G Research and Innovation Lab, Swinburne University of Technology, with the operational mmWave exposure system inside the chamber.

Figure 4

A disposable weighing boat dish filled with saline solution, alongside its corresponding thermal image depicting temperature rise when exposed to 26 GHz radiation.

Figure 5

(A) Establishing a consistent placement for the IR thermal camera at a fixed distance on the rotatable mount to ensure consistent temperature distribution readings. (B) Utilising the 2XT Radiation Monitor, a wearable device for RF-EM field monitoring during the experiment, with frequency ranges for both E-field from 900 kHz to 60 GHz and magnetic (H)-field from 27 MHz to 1 GHz.

Figure 6

(A) Prepared saline solutions with varied NaCl concentrations by mixing distilled water and adding NaCl. (B) Conductive gel for ultrasonic and ECG; we transferred 6.5 mL of each solution to disposable weighing boat dishes measuring 30 mm × 30 mm (C) using a syringe. These dishes were then placed at the focal spot of the antenna with a spot diameter of 10 mm.

Figure 7

(Top): Temperature increase over time. (Bottom): IR images depicting the thermal distribution of 86 mM NaCl saline solution exposed to 26 GHz radiation via a spot-focusing lens horn antenna. Concentrated heat at the focal point reflects gradual heating over time, with the corresponding temperature rise shown on the colour scale. Note: Figure 7, Figure 8, Figure 9 and Figure 10: experiments conducted with a forward power of 26 ± 1 dBm (≈400 mW).

Figure 8

(Top): Temperature increase over time. (Bottom): IR images depicting the thermal distribution of 171 mM NaCl saline solution exposed to 26 GHz radiation via a spot-focusing lens horn antenna. Concentrated heat at the focal point reflects gradual heating over time, with the corresponding temperature rise shown on the colour scale.

Figure 9

(Top): Temperature increase over time. (Bottom): IR images depicting the thermal distribution of 428 mM NaCl saline solution exposed to 26 GHz radiation via a spot-focusing lens horn antenna. Concentrated heat at the focal point reflects gradual heating over time, with the corresponding temperature rise shown on the colour scale.

Figure 10

(Top): Temperature increase over time. (Bottom): IR images depicting the thermal distribution of conductive gel exposed to 26 GHz radiation via a spot-focusing lens horn antenna. Concentrated heat at the focal point reflects gradual heating over time, with the corresponding temperature rise shown on the colour scale.