Low uncertainty broadband EMC measurement using calculable precision biconical antennas

It has been extensively studied and reported that uncertainties as low as 0.11 dB for antenna factor (AF) characterization can be achieved using FitzGerrell (1986) dipole antennas. Although it has been suggested to use these dipoles for swept frequency measurements, broadband biconical antennas have not been investigated and reported in literature in a similar manner. A pair of precision biconical antennas was constructed to investigate this possibility. The antennas were numerically simulated in the frequency range of 30-300 MHz above an infinite conducting ground plane and in free space. The numerical results were combined with the measured S-parameters of the baluns to give the theoretical site attenuation. It has been shown that the standard site method adopted by ANSI C63.4 can have systematic errors in normalized site attenuation larger than 4 dB using free-space biconical AFs from 30 to 300 MHz. The numerical approach described in this paper is shown to be capable of providing theoretical site attenuation values that are within a fraction of a dB of measured results