In this live demonstration from DesignCon 2023, the performance of a Samtec high-speed cable system is measured by the world’s first scalable VNA. Matt Burns (Technical Marketing Manager, Samtec), and Mike Resso (Signal Integrity Application Scientist, Keysight) explain the demo and equipment.
The scalable VNA is Keysight’s Digital Interconnect Test System, with 16 ports that are expandable to 32 ports at 53 GHz. In this demonstration, Mike has calibrated all 16 ports of the Keysight PXI-VNA up to 53 GHz so that a very precise sine wave is output from each distinct channel. In return, the Vector Network Analyzer measures all transmission and reflection signals and uses this information to calculate all scattering parameters (s-parameters). The post-measurement processing is done by the signal integrity specialist software called “Physical Layer Test System.” This enables the signal integrity engineer to review not only frequency domain details of the Device Under Test (DUT), but also eye diagrams, RLCG, and Channel Operating Margin (COM). The eye diagram shown is optimized using multi-channel simulation to equalize the channel using automatic Decision Feedback Equalizer (DFE) taps.
The DUT is a Samtec NovaRay® Signal Integrity (SI) Evaluation Kit. The NovaRay high-speed cable system is Samtec’s flagship product in our line of Samtec Flyover® cable assemblies. NovaRay has not only been designed to operate at 112 Gbps PAM4, but it also offers a pathway to 224 Gbps PAM4. At DesignCon 2022 — also in the Keysight booth — we demonstrated a Samtec NovaRay Mezzanine (two-piece, board-to-board connector set) at 224 Gbps PAM4.
The NovaRay SI Evaluation Kit has the ability to test up to eight differential pairs, through the connector and the cable assembly. The Keysight VNA shows the SI performance results of the cable.
The Physical Layer test system software performed a post-measurement analysis on all of the S-parameters that were extracted from the Samtec DUT. Mike pointed out that the software showed:
- the differential insertion loss with very good performance up to 53 GHz
- the differential Return Loss with very low reflections across the entire band
- TDR showing a very well-controlled impedance environment, which is obviously important for these fast data rates.
In addition, we see two eye diagrams, in NRZ and PAM4 formats. The latter is the typical figure of merit that High-Speed Digital Designers use when characterizing these high-speed connector systems. Mike mentioned that “We’ve got some excellent performance coming out of this device, so we’re quite happy with showing this demo. It also shows how we can stress the test equipment with the … finest DUT possible.”
For more information about the NovaRay cable assembly products, go to www.samtec.com/NovaRay.
If you have questions about the demonstration, contact SIG@Samtec.Com.
Here’s a link for more information about the Keysight Scalable Vector Network Analyzer.
And here’s a link to download a free copy of Mike’s “Signal Integrity Characterization Techniques” e-Book.