Yale part of $9M Army project to bring intelligence to electromagnetic spectrum sensing

Professor Arun Natarajan of Yale is among a team of researchers tapped by the Army Research Office to lead the development of low size, weight, power and cost (SWaP-C) systems that can rapidly sense, identify and locate sources of electromagnetic signals in contested environments. Backed by $9 million over the next six years, the academic-industry partnership will work to provide the U.S. military a decisive edge in the arena of electronic warfare.

The project is an interdisciplinary collaboration led by Duke University that also includes researchers from Northeastern University and Raytheon, an RTX business. The project is aptly named RAPTORS, which stands for Rapid Analog Processing for Tactical Observation and Opportunistic Radio Spectrum Access.

Electromagnetic waves are everywhere all the time. They host a wide range of signals carrying information like radio stations, television stations, cellular phone connections, WiFi data and satellite communications, just to name a few. Anything that needs to be controlled wirelessly or transmit information over the air essentially uses a slice of the electromagnetic spectrum. And that does not even account for sensing signals like radar.

Over the last two decades, Natarajan noted that the electromagnetic spectrum has become increasingly crowded.

“Recently, we have several commercial and military wireless applications where things are being done by autonomous vehicles, planes, and boats,” said Natarajan, professor of electrical & computer engineering. “Being able to monitor and control the electromagnetic spectrum has become really important.”

This crowded medium poses a challenge in contested environments like battlefields. Ensuring your communications are clear or that drones remain under control is essential. Recognizing attempts to compromise these signals or detecting incoming adversarial machines is a matter of life and death.

“It is vitally important to understand which activities and users are occupying the spectrum and to identify the frequency bands and patterns of spectrum occupancy,” said Tingjun Chen, the Nortel Networks Assistant Professor of Electrical and Computer Engineering and lead of the RAPTORS project. “We want to be able to scan a large 3D space quickly across a wide frequency range, identify spectrum occupancy, and understand where they are coming from and what they’re likely being used for, while operating within low SWaP-C constraints through a scalable radio architecture with co-optimized hardware, software and algorithms.”

To achieve this daunting challenge, the RAPTORS team will combine several emerging technologies pursued by laboratories at these three academic institutions.

David Smith, the James B. Duke Distinguished Professor of Electrical and Computer Engineering at Duke, helped invent the field of metamaterials, which are materials that gain their properties through their structures rather than their chemistry. These engineered materials are capable of bending and focusing electromagnetic waves in unnatural ways. They can also be rapidly reprogrammed to focus in different directions without moving or sweep through a wide range of frequencies.

These activities will generate a lot of data that needs to be processed quickly and efficiently. To achieve this, the team will turn to Natarajan and Aravind Nagulu, assistant professor of electrical and computer engineering at Northeastern, to build radio frequency integrated circuits that can preprocess the analog signals as soon as they arrive at the antenna. By specially designing these signal processors and machine learning inference engines, the team can move the data processing as close to the metamaterial antenna as possible, providing tremendous benefits in terms of the system’s computing efficiency, size and cost.

“If we’re able to monitor a slice of spectrum much faster, that means that we can monitor a much wider spectrum,” Natarajan said. “This project pushes the envelope of how wide a spectrum can you monitor within a given time, and also how finely you can slice that spectrum.”

Last but not least, control systems for unmanned aerial vehicles will be developed by Miroslav Pajic, professor of electrical and computer engineering at Duke, so that this electromagnetic frequency detector can explore its surroundings in search of weak or intermittent signal sources. Applying controls and decision-making loops will help the final device make intelligent decisions on where to go and what to investigate.

"It will be exciting to see the analog spectral sensing capabilities developed under the RAPTORS program,” said Robert Ulman, program manager at the Army Research Office in charge of RAPTORS. “Resulting metasurface antennas and analog intelligence cores are expected to have a significant impact on future Army spectral sensing, resulting in improved battlespace situational awareness.”

Rounding out the RAPTORS team is industry partner Raytheon. Raytheon will provide guidance on parameters that need to be met, types of signals the device should focus on, and options for the eventual products to be tested in real-world scenarios.