# SDR-Enabled Multichannel Real-Time Measurement System for In Situ EMF Exposure Evaluation
## 4 Conclusions  
The inherent temporal and spatial variability of the forthcoming generation of communication networks will require extensive in situ EMF measurements. To this extent, in this article, we have proposed a frequency-selective, true real-time, in situ EMF measurement system that can be used in the proximity of modern communication devices. The novelty of the approach is based on the capability of the designed system to synchronously measure both the E- and/or H-field components by using an efficient and agile solution destined specifically to highly dynamic stochastic signals. The system is composed of a sensor built from commercial off-the-shelf E-field probes and a multichannel SDR receiver. The simultaneous retrieval of the field components advances the current frequency-selective isotropic capabilities which, until now, were based on electronic switching (delay present) between the sensor elements. In this way, true real-time and spatial isotropic signal captures are possible, on the sub-microsecond time-variability scale. The proposed sensor geometry enables E-field strength retrieval on three orthogonal directions, in a small volume delimited by the sensor tips. The extension of the probe to the A/H field measurement is also briefly  
Figure 14: Time evolution of Ex, Ey, Ez, and Etotal for IEEE 802.11 ax file download (**a**) and file upload 20 MHz (**b**).  
Figure 15: Time evolution of Efor LTE-A (**a**) and 802.11 ax (**b**) experimental scenarios.  
discussed. A simplified analysis of the mutual coupling effect is carried out, showing the low impact of the mutual coupling on the signal level at the output of the probe.  
The probe was connected to a multichannel SDR receiver. The proposed solution was compared in terms of performances, costs, and requirements to a standard solution enabled by SA and a DO. The three instruments' performances were evaluated comparatively based on their sensitivity (noise floor), accuracy, hardware and software requirements, flexibility, and cost. As a result, we demonstrate the similar performances of the proposed measurement system as compared to the traditional approach highlighting its advantages in terms of cost and flexibility.  
Finally, the SDR-enabled measurement system was used for the in situ measurement of signals emitted by a mobile device in the LTE-A and IEEE 802.11 ax communication standards. By using different experimental configurations, the proposed system demonstrates its capabilities in retrieving synchronous recordings of three RF channels up to an 80 MHz bandwidth. By conducting this research, we have demonstrated that the SDR technology offers a cost-efficient, agile solution for simultaneous multichannel EMF measurements that can be used for signals emitted in modern communication standards. The versatility of an SDR based solution was once more demonstrated in the case of a real-time, multichannel system designed for in situ EMF measurement campaigns.  
Conceptualization, A.S., M.D.M. and S.M.; Methodology, A.S., E.S. and M.S.; Software, P.B. and E.S.; Validation, A.S., S.M. and P.B.; Formal analysis, M.D.M.; Investigation, A.S., M.S. and E.S.; Writing--original draft preparation, A.S.; Writing--review and editing, A.S., S.M. and M.D.M.; Visualization, P.B. and M.D.M.; Supervision, S.M. and P.B.; Project administration, A.S.; Funding acquisition, A.S., S.M. and P.B. All authors have read and agreed to the published version of the manuscript.  
This work was supported by a grant of the Romanian Ministry of Education and Research, CNCS--UEFISCDI, project number PN-III-P1-1.1-PD-2019-0500, within PNCDI III.  
The authors declare no conflict of interest.