![]() Measurement procedure was according to ANSI C63.4-2009 1. The EUT had the largest linear dimension (height) equal to 2,3 m. Radiated emission measurements in the frequency range 30 … 1000 MHz were performed in the accredited semi-anechoic chamber at the distances 3, 5, and 10 m from the EUT that was a stable reference source. Can we predict the field strength when the near-field influences measurement results?.Is it reliable to test relatively large objects at 3 m measurement distance?.Is it realistic to assume the inverse proportionality of the field strength to the measurement distance in a semi-anechoic chamber?.In this article we make an attempt to improve our understanding of the following questions: The interested reader is addressed to this excellent review. Related problems, including the history of their development, are discussed by Daniel Hoolihan 3. The discussion is ongoing within the CISPR community. There is also a concern regarding the RE measurements of the relatively large objects at 3 m distance as the results may be influenced by the near-field effects. Measurement uncertainties, reflections from the reference ground plane, compliance of the measurement setup with the far-field conditions, uncertainties of the site validation, etc. Nevertheless, this approach in many cases does not give correct results. This is made in assumption that the field strength decreases inversely proportional to the measurement distance. If the RE limit in the applicable standard is given just for one measurement distance and the tests are performed at another distance it is a common practice to re-calculate the corresponding values, e.g. Radiated emission (RE) measurements in the frequency range 30 … 1000 MHz are usually performed at the open area test sites (OATS) or in the semi-anechoic chambers at the distances 3 or 10 m from the equipment under test (EUT).
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