Full Modal-Admittance Matrix In-Circuit Measurement by Multiple Inductive Probes

In past years, the use of clamp-on inductive probes was proposed for measuring the impedance or admittance at radio frequencies while the equipment under test (e.g., power electronic converters) is in operation. However, previous one-port methods (involving either one or two probes) allow only an approximate determination of the common-mode (CM) or differential-mode (DM) self-impedance, depending on how the probe/s is/are clamped on wires, and requesting (for DM) the disconnection of the CM return wire. Furthermore, with a single port it is not possible to determine the mutual-modal impedance parameter related to mode conversion. In this paper, a recently proposed multiport measurement method, originally intended for physical admittance measurement, is adapted to modal admittance measurements, resulting in a fast and effective solution for the characterization of full admittance matrices in the modal domain. By experimental tests on passive test networks, it is shown that the proposed method provides accurate results of the true CM/DM self and mutual admittances.