Abstract :
Screened enclosures are required to isolate the equipment under test (EUT) from the prevailing electromagnetic environment. However the problems of testing within this type of environment give rise to potential differences between test environments and test houses by factors of the order of ten times greater or smaller than the true emission field strength voltage. This represents ±20 dB or more, in voltage terms. Due to these differences, equipment cannot be reliably validated for compliance or conformance to specifications, leading to increased contractual and operational risks, as systems may meet the required specifications but could be incompatible in service. To address these problems, the Defence Electrical Standardisation Committee (DELSC) through the working group L8/3 have sponsored measurement investigations, into the veracity of radiated emission measurements within screened enclosures. The aim has been to produce an amendment to Defence Standard 59-41 such that: (1) radiated emission calibration and measurement procedures in screened enclosures economically reduce the uncertainty of measurement to within ±6 dB in voltage terms. (2) Provide traceability to a National Field Strength Standard for the first time. The research has been constrained to EUTs up to 1 m3 and over a frequency range of 1 MHz to 1 GHz. The research has been carried out by a consortium led by the National Physical Laboratory (NPL) and includes the Universities of Nottingham and York
