Non-Intrusive Measurement of Two-Port Impedance Parameters by Clamp-on Inductive Probes

Many applications in the field of power electronics benefit from in-circuit impedance measurements, including modelling of electromagnetic interference and stability analysis of control systems. Noteworthy, a non-intrusive characterization of a system can be obtained, in real operating condition, by clamp-on inductive probes. Unfortunately, the characterization of a multiport system requires the measurement of an impedance matrix, which cannot be obtained by currently known one-port in-circuit impedance measurement techniques. Recently, the introduction of a novel inductively coupled technique allowed non-intrusive measurements of admittance matrices. Though the impedance matrix can be found by inversion of the admittance matrix, this operation is subject to numerical errors. Hence, an alternative formulation allowing direct measurement of impedance parameters is presented in this paper. The proposed method is validated using one set of passive networks, and comparing results with those obtained by direct measurement from a vector network analyser, showing good accuracy from 150 kHz to 30 MHz.