FORMULATION OF NORMALIZED SITE ATTENUATION IN TERMS OF ANTENNA IMPEDANCES

The ANSI standard for EMI measurements requires a test site to be validated by measuring normalized site attenuation (NSA), which is a type of transmission loss between two antennas placed at the test site. Investigations are carried out to find rigorous formulae for NSA, which can apply to both horizontal and vertical polarizations. They are obtained in terms of the self and mutual impedances between the antennas. The NSA measurements are found to be appropriate for site validation when using broadband antennas having constant antenna factors. On the contrary, it is theoretically concluded that the original concept of the NSA may not be applicable to the use of tuned dipole antennas, even by adopting the correction factors specified in the existing ANSI standard. NSA requires different correction factors if the antennas have changeable antenna factors. © 1990 IEEE