Excitation of balanced modes in transmission lines using a clamping transformer

A probe for the excitation and sensing of the differential mode on balanced transmission lines is described and characterized numerically and experimentally. The probe is designed to be insensitive to the location of the transmission line within the probe's window such that its use is similar to that of a BCI probe for common-mode injection and sensing. It is thought that such a device will be useful for measurements involving differential data busses such as the CAN bus. A numerical model is developed using the full dispersion characteristics of the ferrite core. The model is verified with measurements and good agreement is obtained between numerical simulations and experimentally measured data. As with conventional BCI probes, the ability of the ferrite core to facilitate the inductive coupling is retained even in the dispersive frequency region of ferrite. The probe geometry is such that a number of such devices can be arrayed to provide a region of uniform magnetic field illumination of a transmission line.