User:HRShami/Ehsan Afshari

Eshan Afshari is an American electrical engineer, researcher and academic. He is Professor of Electrical and Computer Engineering at University of Michigan.

Afshari's research is focused on high frequency circuits and systems for imaging, bio-sensing, and high data rate communication. He has written over 150 papers. He was the recipient of the 2008 DAPRA Young Faculty Award and the 2010 NSF Early CAREER Award.

Education
Afshari received a B.Sc. in Electrical Engineering from Sharif University of Technology in 2001. He then moved to the United States, where he joined California Institute of Technology, completing his M.Sc. in Electrical Engineering in 2003 and his Ph.D. in Electrical Engineering in 2006.

Career
After completing his Ph.D., Afshari joined Cornell University as an Assistant Professor, becoming Associate Professor in 2012. In 2016, he joined University of Michigan as an Associate Professor of Electrical and Computer Engineering. In 2019, he became Full Professor at University of Michigan.

As a result of his research, Afshari has started two companies. In 2015, he founded Teratooth, a company focused on a low cost replacement for x-ray in dental imaging. He later founded AirVine in 2017, which offers low cost, high data rate solutions for indoor communication at 60 GHz.

Research and work
After completing his Ph.D., Afshari changed his research focus to terahertz circuits and systems. When he began research in this area, most of the terahertz systems used expensive and bulky devices such as quantum cascade lasers. Based on the law of conservation of energy and circuit theory, Afshari's team developed a general theory that can predict the theoretical limit of generated power for any targeted frequency on any given process. Furthermore, they discovered a systematic design method for oscillator design in order to get very close to this limit. By exploiting this approach, in 2010, his team demonstrated a 482 GHz oscillator on a standard 65 nm CMOS that could generate 160 μW. This meant that despite that fact that their transistors were slower, they were able to generate ~8,000 times more power at even higher frequency.

After the initial success, Afshari and his team started to push the performance of terahertz circuits in other areas. In 2016, they demonstrated a two-element 940GHz radiator with effective isotropic radiated power (EIRP) of 100μW. One major challenge with mmwave and terahertz systems is their low power efficiency which limits their applications in portable devices. To address this, Afshari and his team combined the circuit theory, device physics and machine learning to design and implement a 200GHz source with an unprecedented 16% DC-toRF efficiency in 2017.

Afshari and his team also conducted research on the noise performance of terahertz sources. In 2017, their team showed a 195GHz oscillator with phased noise figure of merit (FoM) of -197dB at 1MHz offset. This is the best reported phase noise FoM for any silicon-based oscillator above 2GHz. In 2015 we designed and fabricated an array of sources at 320GHz with EIRP of 180mW. This work was also the first fully integrated phased locked radiator on silicon.

Beside these circuit blocks, Afshari and his team have worked on terahertz subsystems. In 2014, their work showed the first 2-D phased array on silicon above 300GHz. Beside high radiated power, their phased array has two important features: it is fully scalable meaning that each element is only connected to its neighbors and there is no global routing at high frequencies. This makes it ideal for implementation of large arrays. Moreover, this phased array can independently control the frequency and the beam direction. These properties are achieved by using a network of coupled radiators. By controlling the coupling blocks in different modes, they could independently control the frequency of the array and the direction of the radiated beam. Using this novel scheme, they implemented a 340GHz phased array with an EIRP of >50mW in a CMOS process.

Afshari and his team have also implemented a few complete terahertz systems. One example is the first fully integrated coherent terahertz imaging system on silicon. Before this work, all similar systems were incoherent and were only able to detect the intensity of the signal for imaging, resulting in a low sensitivity that limits the applications of the system. In their work, by phase locking the transmitter and receiver, they demonstrated a coherent system. This resulted in an 800 times better sensitivity in the imager compared to the best published work before.

Awards and honors

 * 2000 - Presidential Award of National Best Engineering Student, Awarded by the President of Iran
 * 2004 - Dr. Dimitri Award of Excellence in Engineering Education Association of Professors and Scholars of Iranian Heritage (APSIH)
 * 2004 - Best Paper Award in the IEEE Custom Integrated Circuits Conference (CICC)
 * 2008 - Selected to the Cornell’s First Faculty Institute for Diversity
 * 2008 - Defense Advanced Research Projects Agency (DARPA) Young Faculty Award
 * 2010 - National Science Foundation (NSF) Early CAREER Award
 * 2016 - IEEE Solid-State Circuit Society Distinguished Lecturer
 * 2016 - Selected as one of 50 Most Distinguished Alumni of Sharif University
 * 2019 - Best Invited Paper, IEEE Custom Integrated Circuits Conference (CICC)

Selected publications

 * Afshari, E., & Hajimiri, A. (2005). Nonlinear transmission lines for pulse shaping in silicon. IEEE Journal of Solid-State Circuits, 40(3), 744–752.
 * Afshari, E., Bhat, H., Li, X., & Hajimiri, A. (2006). Electrical funnel: A broadband signal combining method. 2006 IEEE International Solid State Circuits Conference - Digest of Technical Papers.
 * Han, R., Zhang, Y., Kim, Y., Kim, D. Y., Shichijo, H., Afshari, E., & Kenneth, O. (2012). 280GHz and 860GHz image sensors using Schottky-barrier diodes in 0.13μm digital CMOS. 2012 IEEE International Solid-State Circuits Conference.
 * Han, R., Zhang, Y., Kim, Y., Kim, D. Y., Shichijo, H., Afshari, E., & O, K. K. (2013). Active Terahertz Imaging Using Schottky Diodes in CMOS: Array and 860-GHz Pixel. IEEE Journal of Solid-State Circuits, 48(10), 2296–2308.
 * Han, R., & Afshari, E. (2013). A CMOS High-Power Broadband 260-GHz Radiator Array for Spectroscopy. IEEE Journal of Solid-State Circuits, 48(12), 3090–3104.
 * Han, R., Jiang, C., Mostajeran, A., Emadi, M., Aghasi, H., Sherry, H., … Afshari, E. (2015). A SiGe Terahertz Heterodyne Imaging Transmitter With 3.3 mW Radiated Power and Fully-Integrated Phase-Locked Loop. IEEE Journal of Solid-State Circuits, 50(12), 2935–2947.
 * Li, G., Tousi, Y. M., Hassibi, A., & Afshari, E. (2009). Delay-Line-Based Analog-to-Digital Converters. IEEE Transactions on Circuits and Systems II: Express Briefs, 56(6), 464–468.
 * Momeni, O., & Afshari, E. (2011). High Power Terahertz and Millimeter-Wave Oscillator Design: A Systematic Approach. IEEE Journal of Solid-State Circuits, 46(3), 583–597.
 * Tousi, Y. M., Momeni, O., & Afshari, E. (2012). A Novel CMOS High-Power Terahertz VCO Based on Coupled Oscillators: Theory and Implementation. IEEE Journal of Solid-State Circuits, 47(12), 3032–3042.
 * Tousi, Y. M., Momeni, O., & Afshari, E. (2012). A 283-to-296GHz VCO with 0.76mW peak output power in 65nm CMOS. 2012 IEEE International Solid-State Circuits Conference.