Events Calendar

MHI/EE-Electrophysics Seminar, Wednesday, November 30th at 2PM in EEB 132

Speaker: David Allstot, University of California at Berkeley

Talk Title: Switched-Capacitor Circuits Research in Wireless Networks and Ultra-low-power Sensor Interfaces

Abstract: Emerging wireless standards aggregate information by selecting combinations of contiguous or non-contiguous channels, thereby enabling wider transmission bandwidths, and hence, higher data rates. Frequency-interleaved analog-to-digital conversion (FI-ADC) is an attractive emerging technique for carrier aggregation receivers because it facilitates an efficient way to dynamically vary the receiver bandwidth in order to address the many possible channel combinations. Compared to their time-interleaved counterparts, the specifications of the samplers in each parallel channel in FI-ADCs are significantly relaxed, thereby resulting in lower overall power consumption in the receiver. This work extends the FI-ADC idea to the quadrature frequency-interleaved oversampled data converter (QFI-ADC) to achieve greater aggregate data rates. Previously, digital-to-analog converter (DAC) and other inter-channel mismatches have limited the performance of QFI-ADCs. We propose a low-complexity element rotation algorithm (ERA) to mitigate DAC mismatches. The ERA is synthesized from the corresponding mismatch transfer function using a rigorous mathematical procedure which is shown to be generally applicable to low-pass, high-pass, band-pass and quadrature ERA's. Simulations confirm that the resulting low-complexity quadrature ERAs have advantages over previously proposed approaches in terms of both performance and hardware complexity. An additional gain calibration technique alleviates image folding due to mismatches between the quadrature DAC elements, which yields higher SNDR.
The original switched-capacitor power amplifier is a polar power amplifier, amplifying a non-constant envelope modulation by linear combination of the amplitude modulation and phase modulation. It has since been extended to operate across multiple supply domains and to operate using quadrature and multiphase signals. The proposed research will be important to extend the SCPA architecture for future applications. For instance, the SCPA can be used as an enabling technology for massive MIMO, where moderate power, highly efficient, versatile transmitter cores with moderate die area are needed. In massive MIMO, hundreds of transmitter chains drive hundreds of antenna elements to form communications beams that enhance data service to multiple individual users. In addition to massive MIMO, the SCPA offers high efficiency for low-power, high order modulation schemes that are being deployed for wireless sensor systems prevalent in the internet of things. Additionally the SCPA can offer enhanced out-of-band rejection by implementing digital filtering directly in the RF front-end circuitry of a transmitter. This can be by means of weighted summation of an array of small SCPAs. Finally the frequency range of the SCPA can be extended.
Finally, research on the use of CMOS ring amplifier circuits in bio-medical and other ultra-low-power sensor networks is discussed. An analog compressed sensing front-end is used to motivate further investigations.

Biography: David J. Allstot received the B.S., M.S., and Ph.D. degrees from the Univ. of Portland, Oregon State Univ., and the Univ. of California, Berkeley.
He has held several industrial and academic positions. He was the Boeing-Egtvedt Chair Professor of Engineering at the Univ. of Washington from 1999 to 2012 and Chair of the Dept. of Electrical Engineering from 2004 to 2007. In 2012 he was a Visiting Professor of Electrical Engineering at Stanford University and from 2013 to 2016, he held a three-year appointment as the MacKay Professor in Residence in the EECS Dept. at UC Berkeley.
Dr. Allstot has advised about 65 M.S. and 40 Ph.D. graduates, published more than 300 papers, and received several awards for outstanding teaching and research including the 1980 IEEE W.R.G. Baker Award, 1995 and 2010 IEEE Circuits and Systems Society (CASS) Darlington Award, 1998 IEEE International Solid-State Circuits Conference (ISSCC) Beatrice Winner Award, 2004 IEEE CASS Charles A. Desoer Technical Achievement Award, 2005 Semiconductor Research Corp. Aristotle Award, 2008 Semiconductor Industries Assoc. University Research Award, 2011 IEEE CASS Mac Van Valkenburg Award, and 2015 IEEE Trans. on Biomedical Circuits and Systems Best Paper Award. He has been very active in service to the IEEE Circuits and Systems and Solid-State Circuits Societies throughout his career.

Host: MHI/EE-Electrophysics

Location: Hughes Aircraft Electrical Engineering Center (EEB) - 132

Audiences: Everyone Is Invited

Contact: Marilyn Poplawski