EMI Data Reduction, Prediction, and Analysis Using Time-Shared Computers

Today´s complex electronic systems require that the Design Engineers pay particular attention to the side effects of Electromagnetic Interference (EMI) upon system operation. To assist the Design Engineer in considering these additional parameters, the Electromagnetic compatibility (EMC) Engineer must furnish useful tools to enable such considerations to be in the basic design. Through the use of the time-shared computer, which is available through a teleprinter terminal, the complexity and drudgery of EMI Data reduction, prediction, and analysis can be significantly reduced when suitable programs are available. This paper presents two typical programs and describes the major operations and operator-computer interplay. The first program describes the solution to a filtering problem and incorporates Fourier analysis, specification limits, desired values of L, C, and circuit values for source and load impedances. In addition to determining the filter insertion loss as a function of frequency, the program translates these requirements into a 50 ohm system to expedite the purchase of ready-made filters. The second program presented may be used in the reduction of EMI data resulting from broadband conducted interference testing using a current probe. The operator may elect several options during the progress of the program and is requested to enter data readings. Upon completion, the computer prints out a complete data sheet and a graph of the values (data readings plus current probe factors) and specification limits versus frequency. Tilt levels (values greater than the specification limit) are included in the data table.