Test & measurement
Fig. 5: Flexible and easy to use deembedding assistant in an R&S vector network analyzer.
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-OPTIMIZED 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,
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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 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!
PIONEERING NETWORK ANALYSIS SINCE 1950 Rohde & Schwarz is a pioneer in network analysis and launched the world’s first vector network analyzer (VNA) – the Z-g-Diagraph – in 1950, followed by several scalar network analyzers, such as the popular SWOB5 in 1979. In 1995, Rohde & Schwarz launched the R&S ZVR, the first computer controlled VNA with state-of-the-art hardware and software. More game-changing solutions followed, including the R&S ZVT in 2005, the first VNA with 8 ports. In 2008, the company unveiled the first 4-port VNA up to 70 GHz: the R&S ZVA. It was the first VNA capable of measuring non-linear differential components, mixers with system errors corrected by magnitude and phase, and group delay on converters. In early 2019, Rohde & Schwarz presented the R&S ZNA high-end VNA, along with outstanding RF performance, it offers exceptional features that include four phase locked independent sources and two local oscillators.
Rohde & Schwarz
www.rohde-schwarz.com
October 2024 Instrumentation Monthly
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