Methods of 100 dB RF performance verification of facility filters

EMI/RFI facility filters specified to 100 dB are used in government and commercial installations to prevent unwanted signals on power lines. The main standard used to measure filter insertion loss (synonymous for matched impedance attenuation), is MIL-STD-220A. But because MIL-STD-220A was developed only for matched impedance communication systems, it has been labeled unrealistic. Since then, other standards and methods have been developed that attempt to model “real world” attenuation by requiring varying source and load impedance. To date, however, none of these measuring methods have replaced MIL-STD-220A. This paper supports the continued use of the much-beleaguered MIL-STD-220A as the preferred choice for high frequency performance characterization. Additionally, this paper illustrates why none of the existing methods are sufficient to fully verify 100 dB attenuation. Furthermore, in recognizing MIL-STD-220A´s shortcomings, this paper suggests the development of a new facility filter standard that addresses power quality issues, critical RF performance factors and filter/shielded room equipment incompatibility issues that previously have not been considered