Error Analysis of a Near-Field Reconstruction Technique Based on Plane Wave Spectrum Expansion for Power Density Assessment above 6 GHz

Abstract

This paper aims to clarify the accuracy of a method for assessing the power density in close proximity to a wireless communication device operating above 6 GHz for the assessment of compliance with radio-frequency exposure guidelines. We focused on a near-field reconstruction technique that estimates the power density in close proximity to a wireless communication device using the results of electric field measurement at a plane several wavelengths away from the device. In this paper, the reconstruction technique was first validated by comparing the results evaluated using this technique with those obtained by computational simulation for the case of a standard horn antenna. Second, the reconstruction errors of the technique were assessed using ten planar array antennas at frequencies from 15 to 100 GHz. Reconstruction errors no larger than 0.35 dB were obtained for the maximum spatially averaged power density at a separation distance of over 0.15 λ from the antennas using an averaging area of λ2 or larger, where λ denotes the wavelength. Finally, the requirement for electric field measurement was also examined, where the combined error for the compliance assessment of the power density was suggested for an actual testing scenario. These results support the standardization of compliance assessment techniques for wireless communication devices operating above 6 GHz, which are expected to be introduced in the near future.