Alum Recognized for Dissertation Solving Bottleneck in Ultrafast Communication Systems

Future wireless networks and artificial intelligence systems will require electronics capable of moving enormous amounts of data at ultrafast speeds. 

For innovative research advancing the communication and information technologies of tomorrow, electrical and computer engineering alum Phat Nguyen has received the Zuhair A. Munir Award for Best Doctoral Dissertation in Engineering at the University of California, Davis. 

The College of Engineering established the annual award in 1999 in honor of Zuhair A. Munir, the former dean of engineering who led the college from 2000 to 2002 and acted as associate dean of graduate studies for 20 years. It honors a doctoral student, their exemplary research and the mentorship of their major professor.

Nguyen received his Ph.D. in 2024. He worked under Professor Anh-Vu Pham in the UC Davis Microwave Microsystems Laboratory, where Nguyen found encouragement and freedom to explore chips capable of pushing the limits of bandwidth, power and signal amplification. 

A current engineering bottleneck for ultrafast communication systems is chips capable of reaching terahertz frequencies, where signal amplification becomes challenging as chip technologies reach their performance limits on gain, bandwidth and output power. Nguyen reinvented the Darlington transistor pair for terahertz circuit applications to overcome this hurdle.

A Darlington pair combines two transistors, a fundamental component of electronics for signal amplification. Typically, a transistor boosts a signal one at a time. In a Darlington cell, a transistor’s boosted signal is fed into the connected transistor, creating a much stronger and faster signal than with one alone.

Darlington pairs have been around since the early 1950s but have struggled due to the inevitability that one of the two transistors will end up under a heavier voltage or current load, creating an imbalance that degrades performance over time. 

“The tricky part is to unlock the Darlington pair’s full potential in advanced semiconductor processes,” Nguyen said. “My thesis suggests a solution to that: the balanced Darlington cell.” 

The balanced Darlington cell features special diodes that synchronize the voltages and currents of the two transistors inside Darlington pairs. Engineers can now design chips and circuits for ultrafast communication systems that have strong amplification without sacrificing power and bandwidth, which are crucial for terahertz communications and AI data centers. 

“It takes time, persistence and hard work to comprehend current limitations, gather insights that spark innovation and eventually prove new findings,” Nguyen said. “These accomplishments would not have been possible without the guidance of my Ph.D. advisor, Professor Anh-Vu Pham, whose unique insights and visionary approaches have been instrumental in my academic journey, as well as the support of my lab mates.”

Pham said Nguyen’s contributions have put his lab on the map for terahertz technologies. Researchers are already turning to the balanced Darlington cell to push the state of the art. With greater speed, power and bandwidth, terahertz chips with balanced Darlington cells could help build a more resilient internet and infrastructure for AI, as well as more advanced radar and sensing technologies for medical tools and weather imaging.

With an initial curiosity in chip design research fostered at the Ho Chi Minh University of Technology in Vietnam, Nguyen found a passion that continued to grow and deepen through his work with Professor Pham in the UC Davis Microwave Microsystems Laboratory. As part of the lab, he spent six years designing, fabricating and testing the terahertz chips with balanced Darlington cells.

“I am truly honored to receive the Zuhair A. Munir award. It is a great validation of my work, contributing to and pushing the engineering field forward,” he said.

Nguyen’s Ph.D. research led to 10 IEEE journal articles and 12 IEEE conference papers. He currently works for Keysight Technologies as an integrated circuit designer.