Events Calendar

Integrated Systems Seminar Series

Speaker: Prof. Ehsan Afshari, Cornell University

Talk Title: Pushing the Envelope: Oscillators beyond the Conventional Limits

Abstract: In this talk, after a brief introduction to our research at Cornell University, we present a novel dual-band oscillator
with low phase noise performance. This idea leads to a VCO with more than 100% tuning range (2.5 – 5.8 GHz)and extremely low phase noise that satisfies the phase noise requirement for all cellular bands while only taking the area of a fixed-frequency oscillator. Next, we show a novel multi-phase/quadrature oscillator based on lefthanded LC-ring. In contrast to traditional designs that couple multiple LC-tanks through MOSFETs, it uses an LC-ring as a single high-order resonator that generates multiphase resonant signal. The proposed oscillator can synthesize multiple phases while maintaining the same phase-noise figure-of-merit (FoM) as a single-stage LC
oscillator.
Next, we introduce a resonant parametric amplifier/oscillator with an enhanced noise performance by exploiting the noise-squeezing effect. Noise squeezing occurs through the phase-sensitive amplification process and suppresses one of the two quadrature components of the input noise. This structure leads to a noise figure around 0dB for a narrowband signal at around 10 GHz in standard 130 nm CMOS process. It can also be exploited to reduce the phase noise of an oscillator by increasing its amplitude noise.
Finally, we show a novel high power varactor-less VCO at sub-mm-wave and terahertz frequencies. This circuit works based on the theory of coupled oscillators in a ring structure and efficiently generates and combines harmonics from multiple core oscillators. Moreover by adjusting the coupling between oscillators, the frequency can be tuned. Using a standard 65 nm digital CMOS process, we show a 305 GHz VCO with ~10% tuning range and 0.7 mW of output power. The generated power is higher than any other CMOS or compound semiconductor source and at the same time shows the highest tuning range among terahertz CMOS sources.


Biography: Biography: Ehsan Afshari was born in 1979. He received the B.Sc. degree in Electronics Engineering from the Sharif University of Technology, Tehran, Iran and the M.S. and Ph.D. degree in electrical engineering from the California Institute of Technology, Pasadena, in 2003, and 2006, respectively. In August 2006, he joined the faculty in Electrical and Computer Engineering at Cornell University. His research interests are mm-wave and terahertz electronics and low-noise integrated circuits for applications in communication systems, sensing, and biomedical devices.
He was awarded National Science Foundation CAREER award in 2010, Cornell College of Engineering Michael Tien excellence in teaching award in 2010, Defense Advanced Research Projects Agency (DARPA) Young Faculty Award in 2008, and Iran's Best Engineering Student award by the President of Iran in 2001. He is also the recipient of the best paper award in the Custom Integrated Circuits Conference (CICC), September 2003, the first place at Stanford- Berkeley-Caltech Inventors Challenge, March 2005, the best undergraduate paper award in Iranian Conference on
Electrical Engineering, 1999, the recipient of the Silver Medal in the Physics Olympiad in 1997, and the recipient of the Award of Excellence in Engineering Education from Association of Professors and Scholars of Iranian Heritage (APSIH), May 2004.

Host: EE-Electrophysics

Location: Hughes Aircraft Electrical Engineering Center (EEB) - 248

Audiences: Everyone Is Invited

Contact: Marilyn Poplawski