The Advantage of Time Domain Analysis for EMC Broadband Measurements

As opposed to narrow band transmission systems (TV or telephone) modern digital electronic systems (e.g. computers) are susceptible primarily not to typical spectrum configurations of the interfering voltages but to the shape of interfering pulses characterized-by parameters all lying in the time domain e.g. peak amplitude, maximum slope, length of maximum slope and pulse area. There are two possible ways to obtain information about interfering pulses and their shape: One way is to measure the amplitude spectrum by a set of narrow band receivers working in parallel and to develop the pulse shape or the significant parameters from the measured spectrum using a frequency-time transformation. The second way is to apply time domain measurement. The most useful method is the acquisition of the interfering voltage by signal sampling combined with an evaluation of the significant parameters by digital computing. Furthermore oscilloscope measurements can be applied. The comparison shows that time domain measurement and analysis has the advantage that it delivers directly and more accurately the pulse shape and any parameters that are significant for interfering effects in broadband systems.