Efficient power to the people

CSE researchers making faster energy-saving circuits

January 29, 2021

As technology becomes more mobile and wireless, people are demanding faster and faster Internet connection speeds—and the electronics industry will have to keep up accordingly. University of Minnesota College of Science and Engineering professor Rhonda Franklin is at the forefront of that revolution.

Franklin’s lab designs and builds circuits and antennas that are used in electronic communication systems, such as those found in cell phones or laptop computers. The researchers are working to create more energy-efficient circuits so that devices can function at higher frequencies, which will be key in creating technology for the next generation of 6G and 7G wireless networks.

Franklin is a part of an all-women faculty team, along with University of Minnesota professor Bethanie Stadler and University of Texas at Dallas associate professor Rashaunda Henderson. The researchers received a grant from the Semiconductor Research Corporation (SRC) in 2018 to explore the use of nanowire technology in circuits operating at high frequencies. Their work is being watched closely by big tech companies like Intel and IBM, which manufacture chips for many devices.

What’s in a G?

So, what are all the “Gs” in mobile or wireless technology exactly?

In 2019, you probably noticed the tiny 5G icon pop up on your phone where it used to say 4G or LTE. 5G means fifth generation mobile network. A higher G typically operates on a higher frequency and promises larger bandwidth, faster download speed, and more reliable Internet connection.

But, you can only use the higher G networks if your device supports the higher frequency. That’s where Franklin’s research comes in.

“Our kind of solutions can result in better performing circuits that carry really fast signals in the upper 10s or even 100s of gigahertz,” said Franklin, who is a faculty member in the Department of Electrical and Computer Engineering. “Those 10s and 100s of gigahertz are what people are discussing for 6 and 7G. As frequency goes up, how we design circuits has to change to accommodate that if we want them to work well.”

Staying connected

In order for our phones to receive and send information, wireless signals must travel through the electrical circuits in the phones’ chips. But as signals run through interconnects—which are like highways that carry a signal throughout a circuit—they can lose their speed and shape, especially when the frequency increases.

“We have to think about how the current flows through the circuit,” Franklin explained. “The current is a signal that looks like a wave."

"We want to make sure that the signal that goes into the circuit looks almost the same as the signal that comes out.”

Franklin and her collaborators have found a way to preserve that speed and shape—ultimately saving energy—by building more efficient interconnects out of nanowires, which are miniscule fibers 1/1,000th the size of a human hair. Building circuits in this manner could open the door for allowing smaller devices to operate at higher frequencies. 

“My dream would be that because we’re finally here,” Franklin said, “the next step is to think about how building more complex circuits that really exploit the capability of this technology can really show it to be a superb way to get high performance, with low energy consumption that can be used for 6G and 7G.”

The realization of this project is a long time coming for Franklin. She’s been thinking about the idea for nearly 15 years. 

But she had to wait for modern technology to catch up—and for the right collaborators. Franklin’s lab designs and makes the circuits using the materials Stadler’s lab manufactures, and Henderson’s lab tests the circuits’ effectiveness at high frequencies up to 325 GHz.

“This is a collaboration that is possible because of the fascinating work [Professor Stadler] and I have been doing with magnetic nanowires and a visit I had the summer of 2018 to UT Dallas for a month with Professor Henderson,” Franklin said. “This is the first time all the right pieces have come together to move forward.”

Story by Olivia Hultgren

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