E-field Measurements below 30 MHz in Military and Automotive EMC Testing - (PPT)

摘要

Monopole antennas have been conceived for use on a large ground plane: - Reproducibility of automotive measurements through monopole antennas mandates the use of a large ground plane; - The setup on the floor should be explicitly allowed by automotive and military standards. Ultra low impedance grounding is necessary in case of use of an elevated ground plane: - Minimize inductance through the use of wide metal sheets; - Values tabulated in Annex J of CISPR 25:2016 are a valid reference but too much severe (i.e. too small) from 20 MHz to 30 MHz. Minimize common mode current along rod antenna cable: - Route the cable perpendicular to the harness and parallel to the floor in order to minimize mutual coupling with EUT and monopole antenna. Intermodulation effects and out of band response of monopole antenna should be investigated: - Relatively strong out-of-band signals might produce spurious in-band responses (this effect is particularly critical if limits are close to the noise floor).