Analysis of the Common-Mode Rejection in the Measurement and Generation of Magnetic Fields Using Loop Probes

Radio frequency magnetic fields are measured using loop probes. Among the aspects of nonideal behavior, a dominant and elusive one is the unwanted response to common-mode excitation. Little attention has been given to this effect in literature and means for predicting its rejection in comparison to the (intentional) differential-mode response are not available. Formulas to describe the common-mode rejection are derived in this paper and the role of the physical quantities (mainly geometry and frequency) influencing this behavior is quantitatively discussed and made evident. Experiments and computations confirming the theoretical predictions are offered.