Automotive electromagnetic emissions measurements

Theoretical modeling and practical measurements are used to investigate the validity of measuring electromagnetic emissions at closer ranges.

The measurement of radiated electromagnetic emissions from vehicles may be carried out in a semi-anechoic chamber (SAC), a fully anechoic chamber, or an open area test site (OATS) and at varying separations of the antenna from the vehicle, typically either 3 m (10 ft) or 10 m (33 ft). There are differences between the available test methods specified in standards and legislation. For example, the European-type approval directive 95/54/EC specifies a fixed antenna height, whereas international standards such as CISPR 22 require that the antenna be swept from 1 to 4 m (3 to 13 ft) to find the maximum signal. There is also concern that the 3-m (10-ft) test distance is not realistic in terms of the “real world” environment due to interactions between the vehicle and the antenna. However, during some tests a 3-m (10-ft) distance is preferred to permit testing to be carried out alongside the immunity work, thus achieving a more cost-effective procedure.