Uncertainties in 3-m radiated emission measurements due to the use of different types of receive antennas

This work describes the results of an investigation into uncertainties in radiated emission measurement results due to the use of different receive antennas. These antennas are used during electromagnetic-compatibility tests of products which must comply with regulatory radiated emission requirements. In the past few years, the standardization International Special Committee for Radio Protection (CISPR) Subcommittee A (SCA) has tried to improve the radiated emission measurements by quantifying most of the uncertainty sources. We deal with the uncertainty due to the free space antenna factor´s inability to fully specify the antenna properties at frequencies up to 1000 MHz. We have simulated and measured the radiated emission of an equipment-under-test (EUT) using various types of receive antennas. The simulated radiated emission measurement results using a biconical antenna give a maximum difference of 1.2 dB in relation to the use of a tuned dipole. The use of bow-tie antennas leads to a radiated emission difference of maximal 2.5 dB in relation to the tuned dipole. Finally, the use of a log-periodical antenna leads to a maximum deviation of 2.8 dB in relation to the tuned dipole. This means that the uncertainty caused by using different types of receive antennas in 3-m radiated emission measurements may be significant, so the presented uncertainty budgets in CISPR 16-4-2 should therefore be reconsidered and expanded.