Today’s excerpt with Chris Scholz, Product Manager, Vector Network Analyzers, R&S North America, focuses on the SI tools that engineers will need to meet the SI challenge in 2016.
Ed: What tools do you see engineers using and how well do they handle this oncoming SI challenge?
Chris: Vector Network Analyzers have the reputation of being complicated and were considered a specialist tool for ultra-precise measurements and for calibration labs. This SI tool technology has changed, for the better.
Today’s modern computing technology and graphic user interfaces arm any lab technician (with minimal training) to produce reliable and trustworthy VNA measurements. So with modern VNAs, you get the best of both worlds: precise measurements to a well-defined reference plane and ease of use of a modern test tool.
This is of special interest for SI applications where test strategies are traditionally centered around time-domain measurements such as eye diagrams, jitter margins, equalizers and time-domain reflectometry. Today’s VNAs can perform all these measurements and the results tend to be more accurate and repeatable than with traditional tools.
Ed: So you’ve seen SI tools evolve in the last, what, 5 – 7 years? What are the attributes that you look for?
Chris: A good VNA natively supports fixture de-embedding techniques.
For RF applications, fixtures have connectors on both sides; this might be different connectors, but as long as a fixture is “connectorized” with a standard coaxial connector, a good VNA does a good job in de-embedding this fixture.
Ed: What de-embedding tool do you use?
Chris: AtaiTec’s ISD.
Ed: What particular design problems have you seen de-embedding technology help your SI engineers?
Chris: One particular challenge that Signal Integrity engineers face is when a fixture can only be accessed from one side. This is a very common problem when using breakout fixtures for example for USB3.1.
Other examples are when characterizing connectors, or when one needs to accurately characterize an FPGA on an evaluation board. Time-domain gating has been used for many years, is easy to apply and works well for well-matched DUTs.
Next Monday: comparing thru-reflect line with in-situ-de-embedding