## 9 Summary and Conclusions  
The paper presents a new method for reconstructing the EMF in the full half-space above a measurement plane as close as 2 mm from the AUT plane by using the well-known field integral equations and SPEAG's EUmmWVx probe [20]. The method was verified using eight antennas developed to validate measurement systems covering the frequency range from 10-90 GHz. These antennas were selected as they were developed with the intention to pose a challenge for the measurement systems at close distances to the antenna structure. In addition, different noise levels were investigated, with each modeled according to the physical conditions inside the EUmmWVx probe. Finally, the approach was validated with measurements of four different antennas.  
The results show that deviations between reconstruction using FT and simulations were within approximately 0.7 dB for the evaluated distances,ranging from 2.1-150 mm from the antenna for noise levels of \(-\)24 dB and smaller. These deviations are marginally higher for the antennas operating at 10 GHz, where a measurement distance of 4-6 mm, corresponding to \(0.14\,\lambda-0.2\,\lambda\), was required to achieve similar error levels. When comparing FT from measurements close to AUT with direct measurements at the same distance, the results were within 0.6 dB for all four tested antennas.  
The results demonstrate that the new FT method is applicable for compliance assessment and can lead to substantial time savings since the number of required measurements can be dramatically reduced. For example, in cases in which exposure measurements on six surfaces are required, fields on 12 planes should be measured so that, after phase reconstruction, the obtained phasors on the measurement planes return the radiated power. Using the developed algorithm, measurement on one surface is sufficient for obtaining the phasors in the near-field domain and subsequently propagating them to all other five surfaces. Moreover, the possibility of placing the reconstruction surface very close to the AUT reduces the required number of measurements dramatically. For instance, for the example _SlottedHorn10G_, a grid of 8 \(\times\) 8 measurement points with \(0.25\,\lambda_{10\,\mathrm{GHz}}\) resolution was enough to capture 98% of the radiated power. A 12 \(\times\) 12 grid with \(0.25\,\lambda_{30\,\mathrm{GHz}}\) resolution captures 97% of the radiated power in the _DipoleArr30G_ example, and in the _PatchArray60G_circular_ case, a 10 \(\times\) 10 grid suffices to sample 96% of the radiated power.  
This approach results in a very fast demonstration of safety when the device is operating at the head. All assessments are limited to one surface at the closest distance, with the advantage that it is the smallest surface and has the best signal-to-noise ratio. As a rule of thumb, measuring one plane took roughly half an hour to one hour on a cDASY6 system (SPEAG, Zurich, Switzerland) for the investigated antennas; on a state-of-the-art desktop computer, phase reconstruction took few minutes, and evaluating different planes using FT only took a few seconds.  
Conceptualization, N.K., E.N. and S.P.; Methodology, S.P. E.N.; Validation, S.P. and A.F.; Formal Analysis, S.P., A.F., and J.X.; Investigation, S.P.; Resources, N.K.; Writing--Original Draft Preparation, S.P.; Writing--Review & Editing, S.P., A.F., J.X., E.N. and N.K.; Visualization, S.P. and A.F.; Supervision, N.K.; Project Administration, N.K. All authors have read and agreed to the published version of the manuscript. This research received no external funding. The authors would like to thank [PERSON] for performing all the measurements. The authors declare no conflict of interest.