Dual Degree Ph. D. Alum in ECE 

“My Ph. D. was very challenging, but immensely rewarding” - interview with Shaolong Liu

 Shaolong Liu 

Shaolong Liu started his Ph. D. in the 2012/2013 academic year, in Electrical and Computer Engineering. He developed his work with advisors Prof. Jorge Fernandes, from Instituto Superior Técnico in Lisbon and Larry Pileggi, at the Carnegie Mellon’s Electrical and Computer Engineering Department. He shared with us his thoughts on the dual degree Ph. D. experience, now that he is already working as design engineer. 

CMU Portugal – You just began your professional career, what are you working on?

Shaolong Liu – I am an analog design engineer at Analog Devices. We design, manufacture, and market a lot of high performance analog, mixed-signal, and digital signal processing integrated circuits, that are used in almost all kinds of electronic equipment.

CMU Portugal – Does your work align with your research interests?

Shaolong Liu – Yes, very much. I was already interested in analog/mixed-signal circuit design, ultra-low power design, data converters and analog signal processing. 

CMU Portugal – Your thesis is called “SAR ADCs Design and Calibration in Nano-scaled Technologies”. Can you tell us more about it?

Shaolong Liu – The research focuses on replacement of traditional analog signal processing by digital ones. The analog-to-digital converters (ADCs) are necessary for interface between the analog world and the digital one, enhancing their speed, resolution and power efficiency. Still there is the issue of optimization of the design, due to device mismatch, thermal noise and reduced voltage headroom of current technologies. In this work, we investigated the impacts of offset mismatch, comparator noise and capacitor mismatch on high-speed Successive-approximation-register (SAR) ADCs. A set of techniques were proposed, such as an analytical model to estimate the resolution and predict the yield of Loop-unrolled (LU) SAR ADCs with presence of comparator offset mismatch, a background calibration technique to resolve the comparator mismatch issue and an extended statistical element selection (SES) calibration technique is proposed to calibrate the capacitor mismatch. Two prototypes were developed to validate the concept, which proved successful.

CMU Portugal – What would you call your main achievements during your doctorate?

Shaolong Liu – My Ph. D. work studied the analog-to-digital converters (ADCs), which are fundamental blocks for almost all modern electronic and communication systems. We investigated one of the mainstream type ADC in the era of nano-scaled technologies. Our theoretical analyses pointed out some directions for improving the performance of this type of ADCs. The results were demonstrated by two implemented prototype ADCs with state-of-the-art performance achieved. These works have led to one top-tier journal publication and one pending top-tier conference publication.    

CMU Portugal – What would you say are the main aspects of the CMU Portugal Ph. D. dual degrees?

Shaolong Liu – It was a great privilege to study in two great universities, CMU and IST in my case, on both sides of the Atlantic. We benefited significantly from the collaborations with our advisors and colleagues on both sides, learned a lot from different cultures, and, again, made many great friends.

CMU Portugal – How do you describe your Ph. D. experience and would you recommend this opportunity to other students?

Shaolong Liu – I found my Ph. D. very challenging, but immensely rewarding. The experience not only shaped the depth and breadth of my knowledge and capability but also offered me great chances to meet many great people. Yes, I will recommend it and I would be happy to help anyone in this community within my capability, if needed.


November 2017