Making waves in RADAR history

Rohit Rangaraj and Tarun Cousik M.S.’24 are making waves in RADAR history. 

At the 2025 Institute for Electrical and Electronics Engineers (IEEE) RADAR Conference in Poland, the duo put forward exciting new algorithms for hybrid antenna arrays that enable them to achieve performance that rivals fully digital arrays, reducing cost and power consumption with minimal loss in performance.

For their cutting-edge work on behalf of Wireless@VT, the pair won the IEEE AESS Radar Challenge.

Forming new beams

Beamforming is a signal processing technique applied to a group of antennas to focus energy in specific directions, like cupping your hands around your mouth to project your voice. Hybrid beamforming is quickly gaining traction as an alternative to fully digital arrays.

It uses a smaller number of digital channels combined with analog phase shifters; this reduces cost and power, but hybrid systems often struggle to match the precision and interference suppression capabilities due to the inability to observe information at every antenna. 

“The question we asked was simple: could we recover the missing information and close the performance gap? The answer came from a somewhat unexpected place – matrix completion,” Cousik said. “It’s best known for its role in the Netflix Prize where it was used to predict missing movie ratings based on partial data. Our team realized that hybrid arrays face a similar challenge. Their ‘missing’ digital observations form an incomplete matrix, so by treating it as a completion problem, we were able to develop specific algorithms that infer or predict the lost information and reconstruct it to the best of its ability.”

The results were striking. Using the algorithms, their hybrid array achieved performance gains of 20 to 100 times over conventional approaches, demonstrating that data science can bridge the gap between hybrid and digital systems, rather than advanced hardware.

“I can’t say enough how impressive the work of Cousik and Rangaraj is on this topic,” said Jon Kraft, senior staff field applications engineer for Analog Devices and judge of the Radar Challenge. “Their work brings many of the advantages of digital beamforming into the much more practical realm of hybrid beamforming. This is particularly relevant in dealing with intentional and unintentional sources of radio frequency interference in radar, cellular, wireless local area network, and internet of things applications.”

Going beyond the challenge

A senior electrical engineering student focused on radio frequency and microwave engineering, the Radar Challenge was the perfect way for Rangaraj to flex his wireless muscles after completing his summer radar mmWave internship at Texas Instruments.

He connected with Cousik during ECE 5674 last fall, who looped him into working on the Radar Challenge. After their win, Rangaraj has been inspired to continue his education at Virginia Tech by pursuing a Ph.D. with Jeff Walling, associate professor and director of the Multifunctional Integrated Circuits and Systems Group.

“Getting to learn cutting-edge theory and pushing the boundaries of what has been explored and practically implemented felt very empowering,” said Rangaraj. “This work has motivated me to pursue further fundamental research in spatio-temporal signal processing, and to explore where we can take advantage of these techniques in the modern landscape of communications and sensing.”

Rangaraj will re-join Cousik and five new senior electrical engineering students – Charles Early, Eliot Turner, Elias Charron, Fetra Ramiandrisoa, and Danial Mahmoudi – under the direction of Walling in next year’s Radar Challenge. They will build on the current work and advance hybrid beamforming research.

This work was supported by the following collaborators:

NOTE

This research was partially supported by the U.S. Department of Commerce’s National Telecommunications and Information Administration (NTIA) under the Public Wireless Supply Chain Innovation Fund Grant Program (Award # 24-60-IF2415: ASPEN - Advanced Signal Processing Enhancement for Next-Generation Open Radio Units), administered by the National Institute of Standards and Technology. 

Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the U.S. Department of Commerce’s National Telecommunications and Information Administration (NTIA).