Characterization of Terminating Impedances Using Contactless Vector Network Analysis

Scattering parameter measurements play an important role in solving EMC problems as they represent a universal method for determining the high frequency behaviour of a test object. The inconvenience regarding these measurements is that a suitable contacting for the system-under-test is usually necessary but difficult to realise. Contactless vector network analysis (CVNA) methods could improve the situation for certain areas of application. One of these methods provides full two-port CVNA and uses a special sort of current probe, so-called impedance probes, as contactless couplers that can simply be placed around the short-circuited connection terminals of a test object. However, the system-under-test has to be disconnected from its external wiring to perform the measurements which is inconvenient in most cases. In this paper, an expansion of the CVNA method using impedance probes is presented that allows to characterize the external wiring as terminating impedances and thus making it possible to de-embed CVNA measurements of wired test objects.