Whole-vehicle radiated EMI immunity tests in automotive EMC: establishing and calibrating the test field

In EMI immunity testing, the test fields used to expose the device under test must be calibrated so that the levels of exposure can be controlled and maintained at the values required by the test specification. In testing a whole vehicle this can be particularly difficult; the large, usually metallic, structure of the vehicle can couple to the test antenna or field generator and change its characteristics, thus changing the exposure. The author discusses the difficulties of EMI immunity testing for whole vehicles. Calibration of the incident test field is discussed, including the advantages of precalibration rather than monitoring at the device under test; shielded enclosure effects; and calibration accuracy. Also discussed is incident field correction for field generators and radiators with EM field antennas, H-field generators and E-field generators all being dealt with