• • • TEST & MEASUREMENT • • •


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 automatically generates a comprehensive test report, with an overall pass/fail grade for the cable under test, saving lots of time, minimizing human error and letting users focus on analyzing results.


Test plan generation The VNA and switch platform are often controlled and programmed separately. When an R&S VNA is extended with R&S OSP switches, only the VNA has to be controlled. The R&S OSP switch matrix is automatically detected as a port extension and is controlled by the VNA. R&S ZNrun Cable Test Client flexibly defines the number of lanes in the test plan and maps the cable connector pins to the physical ports in a multiport VNA system, making the compliance-testing GUI much easier to operate.


Unique time-optimised calibration


The calibration algorithms in the R&S compliance test solution are optimized for maximum speed and minimum cable reconnections, saving effort and time. The proprietary Rohde & Schwarz guided and user-friendly calibration wizard drastically decreases the overall measurement time. Calibrating a 48-port setup for testing QSFP- DD/OSFP 8-lane cables can be done in 45 minutes or less, instead of two working days.


Automated post-processing and


report generation After calibration, all measurements can be done with the push of a button. If a test item is not needed, it can be deselected. R&S ZNrun follows the test sequence and performs all the measurements. When the measurement is finished, the raw data touchstone files are collected and the signal integrity parameters are post-processed. Afterwards, the final compliance report is automatically generated, including result tables, diagrams and overall pass/fail result.


Beyond compliance testing Apart from fully automated compliance tests, R&S ZNrun can perform fully customized tests and post processing. Limit lines can be modified, while measured lanes and metrics can be selected in


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


line customer preferences. For a quick, initial evaluation of the cable, measurement steps can be deselected. Initial plausibility measurements are often done before starting a full compliance test, where the frequency range and sweep time can use custom settings.


Deembedding-assistant


for test fixture removal In general, high-speed cables under test are plugged into test fixtures to create a coaxial connection linking the VNA ports to cable connector pins. The most important part is the accurate deembedding of all test fixtures.


R&S ZNA/B-K2xx options include the highly flexible deembedding assistant in VNA firmware to configure single-ended or balanced fixtures and coupons for lead-in and lead-out traces. The impedance correction function in the deembedding algorithm also helps eliminate the multi-reflection effect from mismatched fixtures to greatly enhance the accuracy and confidence in test results.


Future challenges


Higher data rates and higher lane density in high-speed interfaces are clear trends in AI data centers and infrastructure, making it more and more challenging to deal with crosstalk and interference in high-speed interface designs, for easy and precise multiport testing. Rohde & Schwarz has a turn-key solution with the VNA automation software suite for compliance and moving beyond compliance to characterize both internal and external high-speed cables. Currently, new technologies for next generation specifications such as IEEE 802.3dj/df up to 1.6Tbit/s and PCIe 7.0 up to 128 GT/s are emerging, so stay connected and stay tuned!


[1] Donahue, C., 2021: Method of implementation (MOI) for IEEE up to 100 Gbps interface channel test.


Fig. 5: Flexible and easy to use deembedding assistant in an R&S vector network analyzer. electricalengineeringmagazine.co.uk


By Lilia Smaoui and Bryant Hsu, both from Rohde & Schwarz


ELECTRICAL ENGINEERING • OCTOBER 2024 31


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.


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