Response of a magnetic loop probe to the current and voltage on a microstrip line

This paper presents a method to determine the coupling of the current and the voltage on a microstrip trace into a magnetic field probe located above the trace. The application of different load impedances to the trace yields different ratios between current and voltage and therefore allows to identify the responses of the probe to both values separately. In the ideal case the output voltage of the loop probe should only be caused by the trace current via magnetic coupling, but in reality parasitic electric field coupling leads to an additional probe signal proportional to the voltage on the device under test (DUT).