IEEE Std ANSI-C63.7-2005 pdf download American National Standard Guide for Construction of Open-Area Test Sites for Performing Radiated Emission Measurements
Definitions
For the purposes of this guide, see ANSI C63.14-1998.
General considerations
Section 5.1 through 5.4.5 of ANSI C63.4-2003 list general conditions for test sites and, in particular, OATSs. To summarize, radiated emission tests can be performed in an open, flat area of cleared, level terrain. Alternate sites might include a raised platform; rooftop site; an open area such as a large factory floor, relatively clear of obstructions that could adversely affect the measurements; or an effectively absorber-lined shielded room that is also free of undesired reflections from the walls and ceiling. The preferred test site is an OATS, which is internationally recognized as the standard for making radiated emission measurements (see [B4]). 3
Such OATSs should be void of buildings, electric lines, fences, trees, etc., and free of underground cables, pipelines, etc., except when using a metallic ground plane that isolates the adverse effects of such underground metallic objects. Services to operate the equipment under test (EUT) and the cabling to the receive antenna should be trenched into the earth if no metallic ground plane is used. The depth of the trench should be such that the cabling will not significantly affect the normalized site attenuation measurement. Clause 5 through Clause 8 describe key recommended characteristics of the test site, the ground plane, instrumentation and EUT services, and all-weather covers. These recommendations should be used to ensure adequate test sites. Adequacy is determined by performing normalized site attenuation measurements described in ANSI C63.4-2003, section 5.4.6.
Obstruction-free area
An obstruction-free area surrounding the EUT and field strength measuring antenna is required. The obstruction-free area should be free from significant scatterers of electromagnetic fields, and should be large enough so that scatterers outside the obstruction-free area will have little effect on the fields measured by the field-strength measuring antenna. The definitive test of the obstruction-free area is to perform normalized site attenuation measurements indicated in ANSI C63.4-2003.