Predicted radiated emissions of systems according to the EMC standards with a time-domain EMI measurement system

Abstract

Measurements for full compliance tests according to the EMC standards FCC, CISPR and MIL have to be performed with EMI-Receivers that must show the behavior as given in the standards. In order to predict the electromagnetic interference of a system field simulations are performed in frequency-and time-domain. Today complex systems like computer mainboards or automotive systems consist of various components that show a emission that could be described by statistical models. We have presented a Time-domain EMI (TDEMI) Measurement System that observes the input signal and generates a statistical model. This model is used to obtain a spectrum that can be evaluated under the various detector modes of an EMI Receiver. The TDEMI System reduces the measurement time by about a factor of 50.In this paper it is shown that the Time-domain EMI Measurement system allows to predict electromagnetic interference of a system consisting of several characterized components. A statistical model of the emission of each source and a model of coupling is used to obtain a statistical model that describes the complete system. The statistical model of the emission of a single source can be obtained by measurements or system level simulations. The coupling model is obtained by field solving tools. The resulting statistical model of the complete system is used to obtain a spectrum that can be evaluated under peak, quasi-peak, average and rms detector. Measurements have been performed with drill machine and a laptop as an example of a system consisting of two sources in the frequency range 30 MHz-1 GHz.