The 5th generation of mobile communications is designed to employ both FR1 and FR2 bands throughout the world. The higher frequency bands (i.e., FR2 n257 26.50 - 29.50 GHz) are posing several challenges to operators and national telecom agencies for performing electromagnetic fields (EMF) measurements. In this work we present the design and preliminary evaluation of an FR2 sensor node to measure EMF radiations in urban environments. The design is carried out in an RF circuit design software, i.e., Keysight ADS, where the various nonidealities (i.e., nonlinearities, noise behavior and electromagnetic response) of the various sub blocks of the systems are accounted for. The sensor concept is then implemented in a prototype board technology (i.e., X-microwave) and its response is experimentally verified in the FR2 band.
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This review offers a detailed examination of the current landscape of radio frequency (RF) electromagnetic field (EMF) assessment tools, ranging from spectrum analyzers and broadband field meters to area monitors and custom-built devices. The discussion encompasses both standardized and non-standardized measurement protocols, shedding light on the various methods employed in this domain. Furthermore, the review highlights the prevalent use of mobile apps for characterizing 5G NR radio network data. A growing need for low-cost measurement devices is observed, commonly referred to as “sensors” or “sensor nodes”, that are capable of enduring diverse environmental conditions. These sensors play a crucial role in both microenvironmental surveys and individual exposures, enabling stationary, mobile, and personal exposure assessments based on body-worn sensors, across wider geographical areas. This review revealed a notable need for cost-effective and long-lasting sensors, whether for individual exposure assessments, mobile (vehicle-integrated) measurements, or incorporation into distributed sensor networks. However, there is a lack of comprehensive information on existing custom-developed RF-EMF measurement tools, especially in terms of measuring uncertainty. Additionally, there is a need for real-time, fast-sampling solutions to understand the highly irregular temporal variations EMF distribution in next-generation networks. Given the diversity of tools and methods, a comprehensive comparison is crucial to determine the necessary statistical tools for aggregating the available measurement data.
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With this contribution, the results of the measurement campaign performed with a synchronously distributed antenna array testbed operating at the center frequency of 3.686 GHz are presented. For the first time, to the best of the authors’ knowledge, the electric field distribution induced by coherent downlink transmission was experimentally assessed in the proximity of the target receiver using a calibrated electromagnetic field probe. This allowed to quantify the actual observed electric field gain and the shape of the electric field enhancement region around the target received. It was found that 16 transmitting antenna elements enhance the root-mean-square electric field level by about a factor of two, in a 2.5λ neighborhood of the target receiver. In addition, a possible disruption of the propagation environment due to the probe movement was assessed through the real-time channel state information feedback.
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