Wooley Named Recipient of IEEE Solid-State Circuits Technical
Field Award: Recognized for Pioneering Oversampling Data Converters in
The 2005 IEEE Solid-State Circuits
Technical Field Award will be presented to Bruce A. Wooley for "pioneering
contributions to integrated electronics for analog-to-digital data conversion
in communications systems." Behzad Rezavi, professor of EE at UCLA
commented on Wooley's accomplishments, "Wooley's fundamental research
on analog-to-digital interfaces and, in particular, oversampling converters
has shaped our thinking and provided analytical tools that now have become
an integral part of high-performance design work."
The oversampling simplifies the choice between what needs to be done in
analog, which is more challenging to design, and what needs to be done
in digital. Oversampling is used in cell phones, MP3 players, disk-drive
electronics, video, wireless, ethernet, medical imaging, and instrumentation.
The success of a huge array of pervasive integrated circuit products is
due to the clear understanding and application of these concepts.
Also known as sigma-delta modulators, the robust design characteristics
provided by oversampling converters eliminate stringent component matching
in VLSI. "The technology has revolutionized the world of modern data
conversion systems and is vital for low-cost, fully integrated digital
communication systems," said Kambiz Kaviani of Rambus.
Wooley first worked on oversampled sigma-delta converters while at Bell
Labs in the late 1970s and early 1980s. His research at Stanford University
advanced the state of the art in sigma-delta converters with over a dozen
JSSC papers on this subject. For example, the 1988 paper with Bernhard
Boser describes the design of an audio-frequency sigma-delta A/D converter.
The analysis and measured results in this paper demonstrate that a sigma-delta
converter with a second-order switched-capacitor modulator and a one-bit
quantizer is not only viable, but is the preferred way to implement audio-frequency
A/D converters. Today, the overwhelming majority of data converters for
voice and audio applications are oversampled converters based on sigma-delta
The concept of sigma-delta modulation (also known as delta-sigma modulation)
was first published by researchers at the University of Tokyo in 1962.
According to David Su of Atheros, "The 1988 article with Boser on
oversampling clearly explained how to design it, how to analyze it, and
made it seem simple enough that most readers felt they could do it too.
Because it wasn't patented, designers could do it themselves. People didn't
have to avoid doing what was explained so clearly. Industry could advance
by copying it, adapting it, and improving it." This paper has been
widely cited and is recognized as a JSSC classic. See the accompanying
article on page 5.
Jim Candy, who worked with Wooley in the research division of Bell Labs
in the 1980s, remembers that the development division of the company was
focusing on switched capacitors because in those days they were easy to
make. "The research division was kept purposely isolated from the
development division because we could so easily get dragged into their
emergencies and deadlines. We worked on developing a solution using oversampling,
which is more accurate. We were trying to get away from analog but we
knew we had to have some. Bruce Wooley provided the design for small analog
circuits that we could fabricate alongside the digital in both bipolar
and, more often later, in CMOS."
At the time Bell Labs stayed with switched capacitors in
its ESS5 switch, which became a workhorse of telecom the following decade.
It took the pressure of deadlines to get the development and research
division to finally work together. "The switched capacitor solution
required all the work in analog and had 2 to the 13th power levels. We
had it down to two levels with oversampling. The research effort totaled
almost a decade."
None of the IC experts contacted could comment on Wooley's technical impact
without also mentioning the legacy of Wooley's students. Dave Hodges,
Professor Emeritus at the University of California, Berkeley, said, "At
Stanford, he has guided the research of outstanding students who have
become leaders in their own right." According to Paul Gray, Executive
Vice Chancellor and Provost, University of California, Berkeley, "The
students he has mentored over the years have gone on to make many contributions
in their own careers. It's great to see this recognition of his outstanding
contributions." Some of his graduate students are Bernhard Boser
at UC Berkeley, Behzad Rezavi at UCLA, Sha Rabii and Marc Loinaz at Aeluros,
James Pan at Kendin, Jieh-Tsorng Wu at the National Chiao Tung University
in Taiwan, Katy Falakshahi at New Enterprise Associates, Alirez Shirvani
at Stanford, Robert Drost at Sun, and Louis Albert Williams III at Texas
Graduate students remember Wooley reminding them, "You are not here
to simply do good research. You are here to publish good research."
Students came away believing that in circuit design it's important to
be useful and relevant. To be useful you have to be articulate so that
someone can benefit from your work.
His exacting standards on clear written and verbal communications, his
emphasis on teamwork among his students, and his belief in enhancing academic
and industry collaboration perhaps provide his most lasting contributions.
Even students who did not have Wooley as their primary advisor credit
his support as critical in the development of their thesis work and still
refer to bound notes from his class ten years later.
Wooley's impact is notable in industry as well. David Soo, president and
CEO of Chrontel (a maker of encoders for digital video), credits Wooley's
invaluable networking for the success of Chrontel. "Wooley has been
with us since our inception, encouraging, helping us find out how things
should be done, helping to define products that start with customer requests
always supporting us, even when the business is tough."
The IEEE Solid-State Circuits Technical Field Award was established in
1987 to honor an individual, or team of up to three, for outstanding contributions
to solid-state circuits, as exemplified by benefit to society, enhancement
of technology, and professional leadership.
The award consists of a bronze medal, a certificate, and a cash honorarium
that will be presented at the ISSCC 7 February 2005. The Solid-State Circuits
Award is one of three dozen technical specialties for which IEEE annually
recognizes outstanding worldwide contributors.
SSCS Executive Director
|Bruce A. Wooley
Bruce A. Wooley (S'64-M'70- SM'76-F'82) was born in Milwaukee, Wisconsin,
on 14 October 1943. He received his BS, MS, and PhD degrees in electrical
engineering from the University of California, Berkeley, in 1966,
1968, and 1970, respectively.
From 1970 to 1984 Dr. Wooley was a member of the research staff at
Bell Laboratories in Holmdel, New Jersey. In 1980 he was a visiting
lecturer at the University of California, Berkeley. In 1984 he joined
the faculty at Stanford University, where he is the Robert L. and
Audrey S. Hancock Professor of Engineering and the chair of the Department
of Electrical Engineering. At Stanford he served as the senior associate
dean of engineering and the director of the Integrated Circuits Laboratory.
His research is in the field of integrated circuit design, where his
interests include low-power mixed-signal circuit design, oversampling
A/D and D/A conversion, circuit design techniques for video and image
data acquisition, high-speed embedded memory, high-performance packaging
and testing, noise in mixed-signal integrated circuits, and circuits
for wireless and wireline communications. He has published more than
140 technical articles and is a coauthor of The Design of Low-Voltage,
Low-Power Sigma-Delta Modulators (Kluwer, 1998) and Design and Control
of RF Power Amplifiers (Kluwer, 2003). He also is a coeditor of Analog
MOS Integrated Circuits, II (Wiley, 1989).
Dr. Wooley is a Fellow of the IEEE and a past president of the IEEE
Solid-State Circuits Society. He has served as the editor of the IEEE
Journal of Solid-State Circuits and as chair of both the International
Solid-State Circuits Conference (ISSCC) and the Symposium on VLSI
Circuits. He is also a past chair of the IEEE Solid-State Circuits
and Technology Committee, and he has been a member of the IEEE Solid-State
Circuits Society Adcom, the IEEE Solid-State Circuits Council, the
IEEE Circuits and Systems Society Adcom, the Executive Committee of
the ISSCC, and the Executive Committee of the Symposium on VLSI Circuits.
He was awarded the University Medal by the University of California,
Berkeley, and was an IEEE Fortescue Fellow. He was a recipient of
the IEEE Third Millennium Medal and was recognized for his outstanding
contributions to the technical papers of the International Solid-State
Circuits Conference on the occasion of the conference's fiftieth anniversary.
He was also a recipient of the Outstanding Alumnus Award from the
EECS Department at the University of California, Berkeley.
Sigma-Delta Converter: How It Works
Oversampling is the technique of sampling an analog signal at more
than twice the highest signal frequency. Operating a converter at
a high sampling rate exchanges circuit speed for amplitude resolution.
For example, a 3-bit flash analog-to-digital converter consists
of seven comparators. An obvious way to increase the converter resolution
is to use more comparators. A less obvious but easier approach to
improving the converter resolution (for low-frequency signals) is
to increase the sampling rate.
Sigma-delta modulation can be used as an efficient oversampling
technique that shapes or rearranges the quantization error in frequency.
A sigma-delta converter with a 1-bit quantizer can achieve 16-bit
resolution within the audio frequency band when oversampled more
than 100 times. Sigma-delta A/D converters employ an analog feedback
loop to shape the quantization error away from the signal band of
interest. A digital filter can then remove the "out-of-band"
quantization error and increase the resolution of the converter.
Sigma-delta converters are popular because of their ease of implementation.
These converters can achieve high resolution without precise component