Dissertation Defense
WHAT: Benjamin Vigoda: Continuous-Time Analog Circuits for Statistical Signal Processing in Multiuser Communication
WHEN: Monday, July 21, 2003, 12:00 PM EST
WHERE:
E15-070
Bartos Theatre [map]
Wiesner Building
20 Ames Street
Cambridge, MA
WEBCAST:
http://helix.media.mit.edu/ramgen/encoder/highlive.rm The link will become active on the date and time scheduled for this event.
DISSERTATION COMMITTEE:
Neil Gershenfeld
Professor of Media Arts and Sciences
MIT Media Laboratory
Anantha Chandrakasan
Associate Professor of Electrical Engineering and Computer Science
MIT
Hans-Andrea Loeliger
Professor of Signal Processing
ETH, Zurich, Switzerland
Jonathan Yedidia
Research Scientist
Mitsubishi Electronics Research Laboratory
ABSTRACT:
This thesis proposes that it is a good idea to build some computers using
continuous-time analog circuits. Digital computation squanders continuous
degrees of freedom. A principled approach to recovering them is to view
analog circuits as propagating probabilities in a message passing
algorithm. Within this framework, analog continuous-time circuits can
perform robust, programmable, high-speed, low-power, cost-effective,
statistical signal processing. This methodology offers the possibility of
adaptable/programmable radio front-ends at frequencies where software
radio would be cost and power prohibitive. Other potential application
areas include ultra-wide-band, high-speed interconnect, optical
communications, and communications for distributed computing.
Many problems must be solved before the new design methodology can be
shown to be useful in practice: continuous-time signal processing is not
well understood. Analog computational circuits known as "soft-gates"
have been previously proposed, but a complementary set of analog memory
circuits is still lacking. Analog circuits are usually tunable, rarely
reconfigurable, but never programmable.
The thesis develops an understanding of the convergence and
synchronization of statistical signal processing algorithms in continuous
time, and explores the use of linear and nonlinear filters and wave-guides
for analog memory. An exemplary embodiment called the Noise Lock Loop
(NLL) using these design primitives is demonstrated to perform
direct-sequence spread-spectrum acquisition and tracking functionality and
promises order-of-magnitude wins over digital implementations. A building
block for the construction of programmable analog gate arrays, the
"soft-multiplexer" is also proposed.
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