Validation of completely absorber lined chambers with an optically driven antenna and free space antenna factors

In many cases completely absorber lined chambers (CALCs) do not seem to comply with the normalized site attenuation (NSA). For a successful validation two steps have to be taken: (1) apply free space antenna factors (AF_FS); and (2) check the NSA of a volume which represents the equipment under test (EUT). The reason for step 1 has already been clarified in previous work. The reason for step 2 is prescribed by EN 50147: `Alternative test site suitability with respect to site attenuation´. However, this method appears not to be as suitable as announced. The main reason is that the method includes the use of classical EMC-antennas like the relatively large biconical antenna; one of the prescribed set-ups has the antenna tip only 0.30 m above the groundplane. Noncompliance is also found in relatively small rooms like the 3 m wide compact room, where the antenna distance to the wall is critical as well. The essence of this work is that the problems are not caused by the CALC; if the classical transmit antenna is replaced by a small optically driven antenna the problems can be solved