Influence of Directivity Pattern of Bilog Antenna to Radiated EMI Measurement Uncertainty

EMC test houses are obliged to derive the uncertainty budget of their measurements. One of these measurements is radiated EMI measurement. Selection of the receive antenna is an important uncertainty source in such a measurement. Choice of Bilog antenna instead of half-wave dipole is convenient due to its broadband properties, but it can influence the total uncertainty of the measurement. Bilog antenna is directional antenna; its directivity pattern (normalized radiation pattern) is different to the dipole´s one. Because all the theoretical calculations consider a dipole and its properties, the use of Bilog can cause additional error, which increases the measurement uncertainty. Analysis of this influence is the aim of this paper.