Analysis results on modeling the effect that source and loadimpedances have upon the predicted emissions from printed circuit boardsare presented. It is shown that, while controlling circuit geometries isimportant, knowing what effect the impedances of the signal source andthe load will have upon the radiated emissions and being able to controlthose effects are also important. It is demonstrated that these twofactors can change the predicted emissions quite dramatically. In thecase of short tracelengths, emissions can be controlled through circuitgeometry quite acceptably, the distance to the ground plane being thecircuit board geometric variable that gives the most control.Unfortunately, when the tracelengths approach a quarter wavelength ofone of the higher harmonics of the fundamental frequency, circuit boardgeometry does not have as much of an effect. At longer tracelengths, onemust consider controlling the source and load impedance in order toreduce unwanted emissions. In addition, when only real resistive loadsand sources are considered, the emissions from the circuit may actuallybe 10-15 dB higher than was presumed
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