OREGON STATE UNIVERSITY

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CMOS Switched-Capacitor Circuits: Recent Advances in Bio-Medical and RF Applications

KEC 1001
Monday, October 31, 2011 - 4:00pm to 4:50pm
Speaker Information
David J. Allstot
Professor
Department of Electrical Engineering
University of Washington

The switched-capacitor technique has been used in high-volume data conversion and signal processing ICs for more than three decades. It is also ubiquitous in RF transceiver circuits because it uses capacitors, which are area-efficient native devices in CMOS technologies, and MOSFETs operating as switches.
 
The RF power amplifier dissipates a large fraction of the total power of a transceiver because of its low efficiency. Despite more than two decades of intensive research, the challenge of on-chip RF PAs with high efficiency in digital-friendly CMOS technologies has not been met. Switching PA topologies with relatively high efficiency have gained momentum, and relatively high output power is being delivered using power combining techniques. Supply regulation techniques have enabled higher efficiency when amplifying non-constant envelope modulated signals. A new paradigm—the switched-capacitor RF power amplifier—which meets many of the remaining challenges is described.
 
Body-area-networks (BAN) that integrate multiple sensor nodes in portable and wearable bio-medical systems are revolutionizing healthcare. A typical BAN comprises several bio-signal and motion sensors and uses ultra-low-power short-haul radios in conjunction with nearby smart-phones or handheld devices (with GPS capabilities) to communicate via the internet with a doctor or other healthcare professional. Higher energy efficiency is critical to the development of feature-rich, wearable and reliable personal health-monitoring systems.
 
The amount of data transmitted to the smart-phone increases as more sensors are added to the BAN. Because the energy consumed for RF transmission is proportional to the data rate, it is advantageous to compress the bio-signal at the sensor prior to digitization and transmission. This energy-efficient paradigm is possible using compressed sensing—a new sampling theory wherein a compressible signal can be acquired using only a few incoherent measurements. For ECG signals, for example, compression factors up to 16X are achievable which means similar reductions in energy consumption. The second part of this talk will overview compressed sensing techniques and describe a switched-capacitor analog front-end for bio-signal acquisition.

Speaker Bio

David J. Allstot received the B.S. from the Univ. of Portland, the M.S. from Oregon State Univ. and the Ph.D. from the Univ. of California, Berkeley. He has held several industrial and academic positions and has been the Boeing-Egtvedt Chair Professor of Engineering at the Univ. of Washington since 1999. He was Chair of the Dept. of Electrical Engineering from 2004 to 2007. Dr. Allstot has advised approximately 100 M.S. and Ph.D. graduates, published about 300 papers, and received several awards. He has also been active in service to IEEE.