Influence of measurement antenna scattering on the radiated electromagnetic field

The prediction of the radiated electromagnetic field from printed circuit boards and/or parts of electronic systems is dealt with by more and more publications. Numerical techniques such as the method of moments are used to solve highly complex mathematical expressions. The article shows that for simple structures a good compliance with measurement results can be achieved. However, one has to be aware of mismatches of about 20 dB /spl mu/V/m in the specific frequency band, which seems to be caused by incorrect models used in the chosen analysis technique. One possible reason for these mismatches is analysed. The theoretical background is described and illustrated by real benchmarks. The first assumption for the reason of these mismatches is often the inaccuracy of modelling the digital and/or analog devices, but only small changes occur after modifying them. Moreover, it can be stated that in the case of fully theoretical examples, which could be solved for analytically, the compliance between the numerical and analytical solution is nearly perfect. Therefore, we conclude that the measurement environment causes the mismatches.