Quantifying automotive RFI

Automotive electrical components, such as motors and microprocessor based circuitry, cause voltage and current disturbances in their power supplies when operated. These disturbances generate electromagnetic interference (EMI) which is radiated from the harness. The interference may occur across a range of frequencies and can disturb communications in the locality of the vehicle. If the interference is of a significant level at frequencies within the radio broadcast bands then it is called radio frequency interference (RFI). The techniques used to measure RFI cannot encompass every aspect of the interference signal´s frequency and time varying characteristics. Techniques which are most representative of the subjective effects for particular conditions of interference signal characteristics and receiver design are discussed. These include open area testing, individual component testing, measurements at the aerial connector, and SINAD based measurements. A strategy to deal with RFI performance is discussed.<>