Radiated emission field perturbations due to accessories used in the FAR environment at 2, 10 & 18 GHz

Radiated emission measurements are usually performed in a facility that meets the Normalized Site Attenuation (NSA) requirements of standards such as CISPR 22 and ANSI C63.4. These standards allow alternative sites such as a fully anechoic room (FAR) for preliminary measurements before final measurements are taken in an open area test site (OATS). The NSA requirements for both these test environments are evaluated in the absence of necessary accessories, such as the table on which test samples must be supported. Additionally, the standards offer only vague guidance on the materials and construction methods used to build the test accessories. We believe this allows uncertainty to enter the measurement environment that is uncharacterized. This paper reports on measurements of these effects at 2, 10 and 18 GHz, and highlights additional facility and antenna interactions and table materials and shapes vis-a-vis their impacts upon measured electric fields. The paper reviews briefly our proposed technique for measuring the far-field signal perturbations that result from inserting test accessories into the common environments encountered in measuring ITE products using the standard noted above.