Test & measurement


Fig. 3: The VNA firmware from Rohde & Schwarz automatically detects the R&S OSP switch as a port extension. In this example the 4-port VNA behaves like an 24-port VNA. This feature is adopted by R&S ZNrun Cable Test Client.


differential signal paths. IEEE 802.3 cable verification requires testing the transmission (THRU) of each lane and crosstalk for all neighboring lanes: near-end crosstalk (NEXT) and far-end crosstalk (FEXT). For more information, see [1].


When higher data rates are needed, the number of lanes in a cable also increases. Manual testing is repetitive, time consuming and error prone. The main cause is the increased number of reconnections and measurements with a 4-port vector network analyzer (VNA). Testing can take up to several days for each cable, such as eight-lane QSPF-DD/OSFP- cables, where users must perform 256 manual measurements and cable reconnections. A further challenge is post-processing data


collected in line with the standard to determine whether a cable passes or fails. The ever increasing complexity and variety of the metrics in various standard specifications make for a heavy workload. IEEE 802.3 defines the channel operation margin (COM) and effective return loss (ERL) as metrics. Excursion metrics for integrated return loss (iRL) and NEXT/FEXT component-contributed integrated crosstalk noise (ccICN) have been introduced for PCIe.


TIME EFFICIENT TURN-KEY SOLUTION Rohde & Schwarz has developed an automated test solution for high-speed cables to relieve test engineers of time consuming and repetitive tasks. The solution combines the


precision and performance of an R&S ZNB vector network analyzer with the R&S OSP open switch and control platform and the R&S ZNrun VNA software suite for faster, easier and more reliable measurements. The R&S ZNrun Cable Test Client and newly introduced R&S ZNrun-K4xx compliance test automation options make for a straightforward test procedure with three simple steps: set up, calibrate and measure. Each step is optimized to minimize calibration and measurement times. The R&S ZNrun Cable Test Client configures switches, performs all required measurement steps and postprocesses all measurement data in line with the COM, ERL, ccICN, iRL and other standard specifications. The solution


Fig. 4: Measurement results for insertion loss as displayed in the automatically generated report Instrumentation Monthly October 2024


Continued on page 24... 23


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