CORRECTION FACTORS FOR NORMALIZED SITE ATTENUATION

EMI standards require test sites to be validated by measuring the normalized site attenuation (NSA) instead of the classical site attenuation (CSA). Theoretical investigations are, therefore, carried out on the general formulation of NSA and CSA, where chain matrices are introduced to account for the effects of antenna circuits. It is found that the theoretical NSA values given by the standards are based on three assumptions inappropriate to measurements using tuned dipole antennas. Thus, correction is considered requisite for every NSA measurement, when tuned dipoles are employed. In this connection, new correction factors are proposed for various measurement configurations at 3-10-, and 30-m test sites. In addition, numerical evaluations are made on the correction factors applicable to the NSA measurements with antenna factors calibrated at 2 or 3 m above a metal plane.