Worst-Case Crosstalk Measurements of Cables—The Multinetwork Analyzer Method

Abstract

Alien crosstalk (AXT) between Ethernet cables produces interference and poses a potential threat to system security. AXT is challenging to measure in pre-existing installations because of the need for instrumentation at both the near- and far ends. Although commercially available portable equipment for this purpose exists, baluns must be used to excite the balanced modes on Ethernet cables, which restricts the bandwidth and includes the unwanted response of the baluns. Here, a novel measurement system is proposed that does not use baluns. The proposed system uses unbalanced network analyzers that are placed at both ends of the cable run. The analyzers are synchronized and phase locked, and the resulting unbalanced crosstalk measurements are then mathematically converted to balanced and common modes. A new calibration method for multiple network analyzers is presented and validated. Worst-case alien crosstalk measurements of Category 6 unshielded twisted pairs using the proposed system are then presented.