Meeting the NSA Requirement for CISPR 16-1-4 in a MIL-STD-461E Type Semi Anechoic Room

The radiated emissions measurements require different types of anechoic chambers for civil and military EMC standards. An anechoic chamber constructed according to the requirements of MIL-STD-46IE may not meet the requirements in CISPR 16-1-4. Instead of constructing a new semi anechoic room (SAR), an investigation on the possible use of a SAR originally constructed for MIL-STD-461E tests to perform the commercial standard tests was carried out. To achieve the goal, the theoretical normalized site attenuation (NSA) formulation of an open area test site (OATS) is revisited in terms of RX antenna height scan range. The variations in the NSA depending upon the height scan range is analyzed both from a theoretical and measurement point of views. Then the chamber is evaluated according to a modified CISPR 16-1-4 approach. The comparative measurement results are presented.