Jun 20, 2018

Total Field Reconstruction in the Near Field Using Pseudo-Vector E-Field Measurements

Serge Pfeifer, Eduardo Carrasco, Pedro Crespo-Valero, Esra Neufeld, Sven Kühn, Theodoros Samaras, Andreas Christ, Myles H. Capstick, and Niels Kuster, IEEE Transactions on Electromagnetic Compatibility, Volume 61, Issue 2, April 2019, online 19 June 2018, DOI: 10.1109/TEMC.2018.2837897

Exposure assessments in the frequency range above 10 GHz typically require knowledge of the power density level very close, 2 mm, to the radiating source, which can be obtained from the total electric and magnetic fields. However, phase measurements are often not feasible in this frequency range, in particular in the reactive near field. We developed a novel phase-reconstruction algorithm that uses E-field polarization ellipse information on two planes separated by a distance of λ/4. The algorithm’s robustness and accuracy were analyzed and optimized for distances of several fractions of the wavelength λ, and a comprehensive set of realistic exposure conditions was simulated to evaluate the algorithm. For distances greater than λ/5, the error of the spatially averaged peak incident power density is found to be <0.5 dB. Measurements in four different antenna prototypes – made with a pseudo-vector probe (EUmmWV2) – revealed that the simulated deviation of reconstructed average power density was consistently <1.1 dB for distances as small as 2 mm, i.e., smaller than the estimated total experimental assessment uncertainty of 1.4 dB. This demonstrates that the power density can be reliably determined by measurements performed as close as λ/5 to any transmitter.

The scientific and technical impact of the study can be summarized as:

  • A novel pseudo-vector probe, EUmmWV2, has been designed that measures the amplitude and the polarization with negligible scattering as close as 2 mm to the radiating source
  • A novel algorithm for the reconstruction of the full electromagnetic complex vector field, i.e., three vector components and their relative phases, has been developed based on measurements on two planes
  • The approach has been extensively validated by testing complex numerical and experimental radiating sources, and a comprehensive uncertainty budget has been established