Radiated emissions from automotive multiplex bus wiring. The effects of offset voltage

Testing has revealed that a multiplex communication network used in an automotive application is a source of radiated emissions. These emissions were found to cause degradation to reception in the automobile´s entertainment radio. Further study revealed that the emissions were the result of common mode current transients brought about by the imbalance in the outputs of the bus differential drivers. The degree of imbalance was found to be affected by a number of parameters including the offset voltage (voltage drop) between modules communicating on the bus. A simple SABER model of the differential driver circuit and load is used to estimate the radiated emissions from the multiplex bus wiring due to voltage offset between two communicating modules. Comparisons of numerical and measured data are presented