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June 22, 2021

ECE researchers receive grant to develop advanced high-frequency antenna

Written By: Jason Daley

Electrical and computer engineering researchers at the University of Wisconsin-Madison are part of a $1.1 million grant from the Office of Naval Research to investigate advances in full-duplex, high-frequency antenna systems.

 Nader Behdad
Nader Behdad

The recipients of the grant are McFarland-Bascom Professor Nader Behdad and Lynn H. Matthias Professor Barry Van Veen along with UW-Madison PhD alumnus and postdoctoral scholar Hung Luyen, now an assistant professor of electrical engineering at the University of North Texas. The title of the project is “Systems and Techniques for Developing Full-Duplex Multi-Functional HF Antennas.”

High-frequency (HF) radio communication covers frequencies in the three-to-30-megahertz range (which, in a quirk of scientific history, are now relatively low frequencies compared to frequencies used by most wireless devices). These waves have large enough wavelengths that they can bounce between the surface of the Earth and the ionosphere, an ion-rich atmospheric layer 50 to 600 miles above sea level. That allows high-frequency waves to propagate over very long distances, sometimes thousands of miles, without the use of cables, satellites, cell towers or other infrastructure, making them especially useful for military applications and popular with amateur radio enthusiasts.

However, high-frequency communications have some limitations. They require physically large antennas and are affected by nearby antennas and the local environment as well as constant changes in the ionosphere dependent on the time of day, solar cycle, seasonality and other factors. This makes it difficult to establish “full duplex” communications, in which the wireless system sends and receives information at the same time.

 Barry Van Veen
Barry Van Veen

In their project, the team plans to investigate system-level solutions to improve the antenna functions that enable establishing full-duplex communication by optimizing the electronics and improving the antenna’s predictive capabilities. Because HF communications are affected so much by the immediate surroundings, predicting changes in the environment and compensating their effects can help improve the system, especially on something like a moving vehicle or ship at sea.

“There are systems out there right now that people use that can adapt to changes in the environment, but there’s a significant lag time,” says Behdad. “But if you’re transmitting a lot of power, that’s not acceptable, so you need to adapt to the environment much faster.”

That’s where Van Veen’s expertise comes in. He’s developing predictive algorithms that allow HF systems to predict changes in the environment and adjust to those changes much more quickly. “You can’t have an aircraft going 600 miles an hour due north instantly change to going 600 miles per hour due south. Physics doesn’t allow it,” explains Van Veen. “Objects tend to keep moving the way they were moving and measurements of those objects tend to change rather smoothly. So, the idea is to develop algorithms that look at the current data and the past data and translate that into predictions of the properties of the environment in a few seconds. And then that prediction can be used to inform the electronics, which can compensate for the changing environment. That allows us to remain highly efficient even though the environment is changing.”

Militaries around the world are investigating modern, wideband HF communications as complementary systems to satellite communications networks, which are vulnerable to jamming, interception and even anti-satellite attacks.