Friday, February 22, 2013 - 2:00pm to 2:50pm
KEC 1007

Speaker Information

Harish Krishnaswamy
Assistant Professor
Department of Electrical Engineering
Columbia University


Efficient generation of power at mm-Wave and sub-mmWave frequencies in CMOS is a fundamental challenge. Power generation in CMOS is plagued by fundamental trade-offs between output power, efficiency, operating frequency, and linearity. In this presentation, I will present a technology-driven unified formulation of the power generation problem across three orders of spectral magnitude – from RF through mmWave to terahertz. I will then present recent advances in this space at Columbia University.

At mmWave frequencies, device stacking is demonstrated to be a powerful technique that alleviates the speed-breakdown voltage trade-off inherent in all electronics. Furthermore, for the first time, technology scaling has enabled the implementation of switching-type power amplifiers at mmWave frequencies in CMOS, albeit based on new design principles. A new analytical Class E design methodology has been devised that maximizes PAE in the presence of high device-loss levels. Through this methodology, stacked Class-E-like 45GHz PAs in 45nm SOI CMOS achieve 15-20dBm of output power at a world-record efficiency of 35%. A new fully-integrated power combining technique has been developed that enables power-combining of up to 16 elements in one step with high combining efficiency. A power-combined 45nm SOI CMOS PA array achieves 0.5W of output power over 33-46GHz -- a world-record by a factor of 5, and the first watt-class CMOS PA at mmWave frequencies. Finally, a new linearizing architecture has also been developed that combines large-scale power combining, supply-switching and dynamic load modulation to enable high output power and high efficiency under backoff.

At terahertz frequencies, a Maximum-Gain Ring Oscillator topology will be discussed that theoretically maximizes the frequency of oscillation of a terahertz source in a given technology. 220GHz and 320GHz sources in 45nm SOI CMOS will be discussed that operate close to the fmax of the technology. I will then show how the concept of nonlinearity engineering can be used to create terahertz sources in CMOS that achieve mW-level output power along with wide frequency tuning range and acceptable phase noise.

Speaker Bio

Harish Krishnaswamy received the B.Tech. degree in Electrical Engineering from the Indian Institute of Technology-Madras, India, in 2001, and the M.S. and Ph.D. degrees in Electrical Engineering from the University of Southern California (USC) in 2003 and 2009, respectively. He joined the EE department of Columbia University as an Assistant Professor in 2009.

His research group at Columbia, funded by various federal agencies, including NSF and DARPA, and industry, focuses on millimeter-wave CMOS power amplifiers and transmitters, sub-mmWave devices, circuits and systems in CMOS, broadband RF receivers for cognitive radio, and field-programmable, waveform-adaptive RF CMOS transmitters.

He received the IEEE International Solid State Circuits Conference (ISSCC) Lewis Winner Award for Outstanding Paper in 2007. He also received the Best Thesis in Experimental Research Award from the USC Viterbi School of Engineering in 2009, and the DARPA Young Faculty Award in 2011.