Movable Noncontact RF Current Measurement on a PCB Trace

This paper develops a movable noncontact probing method of a radio frequency current on a printed trace based on the electromagnetic induction. The current measurement method is validated by comparing a series of reconstructed periodic and pulse currents with those as known input signals on a microstrip line. According to our measurement, the transfer impedance from the current under measurement to the probe has a linear frequency range from 10 MHz to 2.2 GHz. The reconstruction measurement can be achieved even for a random periodic noise with a duration of 1 ns and a single pulse with a rise time of 2 ns. Owing to the flexible relocation of the probe, the measurement accuracy due to the errors of spatial displacement and the probe placement angle is investigated in detail. It is shown that the dynamic parameters of reconstructed current, such as fall time and rise time, are insensitive to the spatial errors, and instead the amplitudes of both periodic and pulse currents are highly sensitive, especially to a horizontal displacement.