New $2M NSF Research Grant Aims to Expand Wireless Access

A non-reciprocal radio-frequency circulator integrated on a CMOS chip for the first time by Harish Krishnaswamy's research group.
—Photo courtesy of Harish Krishnaswamy

A Columbia Engineering-led research team is bringing society closer to realizing less expensive, high-data-rate wireless access thanks to a new grant from the National Science Foundation (NSF).

Led by Harish Krishnaswamy, associate professor of electrical engineering, the team includes John Kymissis, associate professor of electrical engineering, and Guillaume Bal, professor of applied mathematics, as well as colleagues Amit Lal and Al Molnar of Cornell University. They are one of nine teams to receive a $2 million, four-year research grant to overcome conventional limitations of light and sound waves by focusing on the physical principles of reciprocity and time-reversal symmetry. By effectively breaking the current laws of physics, the team hopes to increase the capacity and accessibility of wireless data. 

“Classical electromagnetic wave propagation is reciprocal, meaning that light and acoustic waves propagate the same way in forward and reverse directions in most materials, which limits the design and functionality of many devices, including wireless,” said Krishnaswamy. “If this fundamental law can be broken, or at least bent, we could build new types of ‘non-reciprocal’ devices for different types of waves with completely new functionalities.”

The team won support for their proposal, “Novel approaches to RF non-reciprocity in semiconductor systems.” Non-reciprocal components, such as circulators and isolators, enable new wireless communication paradigms, such as full-duplex wireless that are otherwise not feasible and promise to significantly enhance wireless data capacity. However, non-reciprocal components are limited by the need for large and expensive magnetic materials, which are incompatible with the silicon-based integrated circuit technologies that power the wireless and computing revolutions.

While recent research has shown that introducing time variance into a material or system can break reciprocity, existing spatio-temporal modulation approaches to realize non-reciprocal components have been fraught with challenges. Krishnaswamy’s team will pursue various multi-physics approaches to investigate semiconductor systems as a material property with the potential to be powerfully modulated to achieve non-magnetic radio frequency (RF) non-reciprocity in silicon-based integrated circuit technologies.

Columbia Engineers Develop the First On-Chip RF Circulator that Doubles WiFi Speeds with a Single Antenna
—Video by Jane Nisselson

Said Krishnaswamy, “If we can enable the breaking of reciprocity at radio frequencies, then it will be possible to have compact, low-cost RF non-reciprocal components and expand the range of the accessible RF spectrum. Such an achievement would go a long way toward meeting society’s need for enhanced access to wireless data and making commercial, wireless devices accessible to a larger portion of the population.”

In addition to research, the team will provide opportunities for students from kindergarten through graduate school to learn about and engage with their findings. These educational opportunities will leverage current programs at Columbia and Cornell, in collaboration with the Liberty Science Center in New Jersey and a number of outreach and diversity programs.

The NSF grant is funded through the organization’s Emerging Frontiers in Research and Innovation (EFRI) program. New light and acoustic wave propagation, or NewLaw, is one of the program’s two research areas meant to rapidly advance frontiers of fundamental engineering research through interdisciplinary teams. The grant will fund 37 researchers at 17 institutions over the next four years.

by Allison Elliott

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