From sensing weapons to measuring jitter

-January 30, 2014

Dr. Daniel Chow is an expert at measuring high-speed digital signals, but he didn’t start his career that way. His work at Apple, Altera, nVidia, and Wavecrest includes defining the design, testing, and validation methodologies for signal integrity and power integrity in high-speed components and silicon devices. At these companies, Chow has consistently pushed the limits of test equipment and explored new challenges in jitter modeling, measurement, and analysis. Through his many DesignCon papers, Chow has shown that you can't rely on any one instrument when measuring jitter, especially with the vaguely-defined category of "bounded, uncorrelated jitter" or BUJ. His leadership measuring signal integrity and power integrity earned EDN readers' choice as the 2014 Test Engineer of the Year.

I first met Chow in 2009, having interviewed him for The Philosophy of jitter where he was featured on the cover of the June issue of Test & Measurement World. The photo, taken at Altera and from the cover, shows Chow surrounded by test equipment—oscilloscopes, BERTs, VNAs—and he likes it that way.

Chow actually had two stints at Altera. The first came after Wavecrest ceased operations. After several years at Altera characterizing serial links in FPGAs, Chow moved to nVidia where he characterized high-speed links in graphics processors video cards. That's a high-volume business compared to Altera's. In From back end to front end, Chow described to me the contrast between the two.

Chow's nVidia stay didn’t last long and he went back to Altera because "Altera presented new and rewarding challenges at 28 Gb/s and beyond which were hard to pass up." Today, Chow is a principal signal integrity engineer at Apple. But, that's about all we know about his work because with Apple being Apple, Chow doesn't say much about what he does now. Because of that job, 2014 is the first DesignCon in many years where he didn't deliver a technical paper. He's still involved in the conference, reviewing technical papers on test and measurement. His last DesignCon paper, "High-Throughput, High-Sensitivity Measurement of Power Supply-Induced Bounded, Uncorrelated Jitter in Time, Frequency, and Statistical Domains" won Chow a DesignCon 2013 best paper award. Although he can’t discuss the technical aspects of his work at Apple, Chow assures us that, as Tim Cook recently said, Apple is working on "great things."

Daniel Chow (second from right) accepts a DesignCon 2013 award from Barry Sullivan at DesignCon 2014.

Although Chow has measured signal integrity and power integrity at four companies, he didn't start his career knowing anything about high-speed serial links. He started as a physicist in graduate school and at Lawrence Livermore National Laboratory.

Chow received his Bachelor's and first Master's degrees at San Francisco State University. After graduating, he went to the University of California-Davis where he earned a second Master's degree and Ph.D. "The UC Davis program is called Department of Applied Science," he said, "but it's strange because the program has a science curriculum but is part of the College of Engineering." The program was founded by Edward Teller, who developed the hydrogen bomb and is often credited as the inspiration for Peter Seller’s character Dr. Strangelove. Lawrence Livermore Lab was, as Chow told me, founded so that Teller could continue the development of thermonuclear weapons. "Although Teller was quite controversial," Chow said," he was a strong believer in education and he wanted his staff to obtain advanced degrees in physics and other sciences." But, because of his controversial history, no physics department wanted to associate with Teller, and that included UC Davis, which started in the 1960s. So, the program became part of the College of Engineering. Teller's program was located in Livermore, Calif. The teachers were also researchers at Lawrence Livermore Lab.

Chow entered "Teller Tech," as it was nicknamed, after completing a master's degree at San Francisco State, where he worked on thin film processes for superconducting circuits that were used by NASA for sensitive microscopic calorimeters. Livermore Lab had a similar program so it was natural for him to continue is education there and at UC Davis. He worked on X-ray sensors but when NASA funding slowed in the 1990s, Chow's work changed from sensing X-rays to sensing Gamma rays. The detectors were sensitive enough such that they could identify the minute differences between fissile materials for power plants and weapons, thus enabling the enforcement of nuclear non-proliferation treaties and arms control programs.

In 2001, Chow was about to graduate with his Ph.D and the people at Livermore wanted him to continue to work there. But, this was around the time of alleged information leaks at Los Alamos National Labs by Taiwan-born nuclear scientist Dr. Wen Ho Lee (later nearly all charges were dropped and he was awarded a $1.6 million settlement by the federal government). Because his mother was born in China, albeit before the Communist revolution, Chow decided to look for work in industry rather than stay with a national lab. "There were rumors that the FBI was going to scrutinize people with Chinese heritage," he said, even though I was a naturalized U.S. citizen." (He was born in Hong Kong. His father was from Hong Kong.)

Chow was discovered by Dr. Mike Li (currently an IEEE Fellow), who was also a physicist, while Li was looking for people with physics backgrounds to work for Wavecrest on signal-integrity. Although Chow had hadn't met Li until 2001, the two had similar backgrounds and knew several of the same professors and researchers. As he tells it "Mike told me that I will work on jitter and love it even though I had never heard of jitter then. I learned everything I know about jitter from Mike."

Daniel Chow accepts EDN's Test Engineer of the Year award from Chiphead at DesignCon 2014. Bill Driver (far left) of National Instruments and Patrick Mannion of EDN (far right) joined them.

The two worked for Wavecrest in the San Jose office doing simulation of high-speed data streams. When Wavecrest folded, Li helped Chow get a job at Altera. "About a month after I started at Wavecrest," said Chow, "we booked a flight to Minnesota to meet the people at Wavecrest's headquarters. That was Sept. 10, 2001." We all know what happened the next day and as a result, Chow and Li rented a car and shared the experience of driving back to California, forming the mentor-mentee relationship that continues to this day.

For winning the 2014 Test Engineer of the Year award, Daniel Chow has designated that a $10,000 grant from National Instruments go to the Thin Film Lab, part of San Francisco State University's physics department.

EDN articles by Daniel Chow
The many faces of jitter
Jitter: Measurement references matter

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