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Ed Lee
Ed Lee
Ed Lee has been around EDA since before it was called EDA. He cut his teeth doing Public Relations with Valid, Cadence, Mentor, ECAD, VLSI, AMI and a host of others. And he has introduced more than three dozen EDA startups, ranging from the first commercial IP company to the latest statistical … More »

High speed designs require new ways to handle Signal Integrity

January 4th, 2016 by Ed Lee
Chris Scholz

Chris Scholz

We recently had a chance to sit down with Chris Scholz, Product Manager, Vector Network Analyzers, R&S North America at German electronic equipment manufacturer Rohde & Schwarz. For those of us who aren’t familiar with Rohde & Schwarz, it’s a worldwide electronics group company with business fields in test and measurement, broadcast and media, secure communications, cybersecurity and radio monitoring/radio location. Based in Munich, R&S was founded in 1933 and has had a U.S. presence for years.

We got together with Chris to hear what was the big design issue his engineers were encountering as 2016 approached. Here’s what he had to say.

Today’s excerpt gives us some background on Rohde & Schwarz and Signal Integrity. 

Ed:   Chris, before we get into the heart of our discussion, it might be good to give us a brief rundown on who Rohde & Schwarz is.

Chris:   Sure, Ed.   Rohde & Schwarz is primarily known for our leadership in RF, microwave and millimeterwave technology. We were founded in 1933 and are based in Munich.  We have close to 10,000 employees.

Ed:  How has Rohde & Schwarz dealt with high-speed measurement and calibration problems?

Chris:  In 1950, we built the world’s first Vector Network Analyzer (VNA) that was used to characterize cables and measure impedance matching for wireless transmitters.

If I compare the challenges that RF engineers face with the issues that Signal Integrity engineers face, I’d say that there are a lot of similarities but also very important differences.

Ed:  Intriguing.  How so?

Chris:  One of the common threads is that frequencies are ever- increasing. To a large extent, that is a result of technology enablers such as RF CMOS.

At the same time, an ever-increasing demand for bandwidth from consumers drives technology to new records. Traditionally the wireless community has led this race for higher and higher frequencies but the gap is closing rapidly. Today’s Signal Integrity engineers routinely deal with frequencies up to 50 GHz, research labs are pushing beyond 100 GHz. These frequencies are very similar to the evolving wireless 5G standards.

Ed:  So what are the crucial differences?

Chris:  The two main differences between wireless technologies and Signal Integrity are that Signal Integrity engineers deal with baseband signals and use simple modulation techniques. By comparison, wireless systems, even “ultra-broadband”, is very narrowband and wireless engineers are forced to develop ever more sophisticated multi-level modulation schemes.

Ed:  So what I’m hearing is that Signal Integrity design issues are surfacing and becoming primary.  And these issues will become or are already critical.

Chris:   Yes.  The Signal Integrity community has seen tremendous change, but I would call these changes more evolutionary than revolutionary.

Throughout the history of Signal Integrity, techniques that were originally applied for wireless systems have helped solve Signal Integrity problems.

A good example for this are pre-distortion and receiver side equalization techniques. Today, multi-level signaling and advanced modulation techniques are modified to help Signal Integrity engineers drive signals at higher speed over larger distances with lower consumption.

Ed:   Where do we see this happening?  And what do we see happening?

Chris: Well, in the test and measurement world, many of our customers start questioning the accuracy of their traditional test tools. Not too long ago SI engineers were satisfied if a measurement matched reasonably well with the expected value. Today we see more and more SI engineers analyzing the measurement uncertainty of their test setup with the goal to minimize the measurement error and to maximize the shrinking design margins.

As a consequence, I also see more and more users turning away from time-domain based channel characterization towards the use of Vector Network Analyzers.


Rohde & Schwarz will be exhibiting at DesignCon at booth #643.  

Next up:  Tools to meet the SI challenge in 2016

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