Investigation of vehicle immunity against RF noise

In this paper, the radiated immunity problem of the Electronic Control Modules (ECUs) on a vehicle is investigated using the transfer function method, which characterizes the system frequency response by measuring the attenuation of the signal through the cable harness. A simple bench test methodology is described to obtain the system characteristics. Based on the findings in the transfer function, it is proven that the immunity of the ECU is reduced at the resonant frequency of the harness since it is with lower attenuation. A countermeasure is then applied to the module to increase signal attenuation and its effectiveness is verified on the bench and vehicle. This method is proved to be quick and efficient in solving the immunity problem in the vehicle electronic system while the cost is minimized.