TTU researchers demonstrate first time-reversal radio

A novel time-reversal based radio demonstrated by a Tennessee Tech University research team this spring stands to answer the U.S. Department of Defense’s need to increase security aboard ships and connectivity between them.

TTU electrical and computer engineering professor Robert Qiu and his team celebrated the successful demonstration of the system with a name that immediately conjures up ideas of time travel, but that actually allows information to travel through difficult environments. The technique answers the challenges of the U.S. Navy and others in the DOD community who can’t transmit radio signals in certain harsh environments, such as all metal-cargo ships.

“Before, no single frequency would allow radio signals to penetrate all-metal or 10-12 inch concrete walls, so you lost the ability to communicate within such an environment,” explained Qiu. “The ships were an ideal testing ground for proving the glory of UWB. The United States is leading the world in this technology and nobody had proved it would work, until now. We proved it.”

Four years ago, the team launched efforts to build the first Ultra Wide Band time-reversal radio test bed, amid doubts from colleagues and government officials that their technique would work.

But Qiu wanted to solve the problem faced in U.S. Coast Guard ships where equipment won’t work under the deck because of the all-metal cargo bay. Searching for hidden weapons of mass destruction and other security threats can’t be carried out without an effective way to send signals through the ship and to others in the fleet.

“We are gamblers; the beauty is to make something work,” said Qiu. “We basically learned to exploit the multipath feature of UWB to increase the data rate and extend the range of the signal.

“Think of a shout and an echo,” he explained. “The original messages comes back to you, in this case, in the form of many multipaths of short waves that we read “backwards” or reversed. We took advantage of the underlying physics to increase the data rate to almost optimum, almost 100 percent.”

Mathematical time reversal methods are based on the premise that if you can reverse a signal, it can then be traced back to its source, somewhat like playing a movie backwards to see its beginning.

In transmitting a signal such as “hello” from a transmitter to a receiver array, each element of the receiver array records and transmits a time reversed (last in, first out) version of the signal. So “hello” is received as "olleh.”

Although the transmitter is complex and costly, the UWB receivers will be low-cost.

“Only a research university can respond to a challenge like this,” said Qiu. “We have 10 undergraduate students in this project, and Ken Currie at the Center for Manufacturing Research, helped us put together a great team.”

When TTU’s team demonstrated the radio to the Department of Defense community, including U.S. Navy, Army and Air Force representatives, research engineer Terry Guo was satisfied, and a little relieved. He left private industry to join the team in order to be a part of the groundbreaking research.

“I was silent for three days,” said Guo. “Despite all our lab work, you cannot simulate real life until you have the chance to test the system for real, so I was really worried this wouldn’t work.”

Qiu says other groups “don’t dare to try to make this radio,” because the delicate equipment cannot be placed in inexperienced hands.

“But I’m a cowboy; I have to take risk,” said Guo.

“When we look back, our whole team contributed to this mission,” said Qiu. “Without the team, the concept of time reversal was a dream. Now, it is a reality.

“We are competing with teams in leading institutions, and we have demonstrated that we can make a difference,” he said.

Involving students in this research ranks as high with Qui and his team as their successes. “We don’t push, we lead,” he said. “There is a lot of pressure, with work day and night and weekly goals, but we teach them how to work under the pressure.

“We show them how the top tier institutions operate, plus we show them how private companies operate with competitive standards,” he added.

Qui, jointly appointed with both TTU’s Center for Manufacturing Research and electrical and computer engineering department, says research with military applications attracts undergraduate students to graduate work, a goal of TTU’s ECE engineering department. He says the key is to seamlessly integrate education and research.

Qui anticipates about 18 months for the technology transfer from the university to the government. At that point, the government takes over and classifies the technology’s uses. Then Qui will turn to other applications with commercial potential.

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