3D reflective microchip could accelerate 6G wireless development

Cornell University researchers have developed a semiconductor chip that will allow ever smaller devices to operate at the higher frequencies needed for future 6G communications technology.

The next generation of wireless communications not only requires higher frequencies and more bandwidth, but also a little extra time. The new chip adds the necessary time delay so that signals sent across multiple arrays align to a single point in space without collapsing.

The team’s paper, “Ultra-compact near-real-time delay to improve wireless channel capacity,” was published on March 6. Nature. The lead author is Bal Govind, a doctoral student in electrical and computer engineering.

Most of today’s wireless communications, such as 5G phones, operate at frequencies below 6 gigahertz (GHz). Technology companies have been aiming to develop a new wave of 6G cellular communications that use frequencies above 20 GHz, where there is more available bandwidth, meaning more data can flow faster. 6G is expected to be 100 times faster than his 5G.

However, one important factor is how the data is relayed, as data loss in the environment increases at higher frequencies. Rather than relying on a single transmitter and a single receiver, most 5G and 6G technologies use a more energy-efficient method: a series of phased arrays of transmitters and receivers.

“Every frequency in the communications band has a different time delay,” Govind said. “The problem we are addressing is decades old: transmitting high-bandwidth data in an economical way and ensuring that the signals on all frequencies align at the right place and time. .”

“It’s not just about building something with enough delay; it’s about building something with enough delay that there’s still a signal at the end,” said senior author and engineering professor Alyssa. Apsell said. “The secret is that we were able to do it without incurring huge losses.”

Working with postdoctoral researcher and co-author Thomas Tapen, Bal designed a complementary metal-oxide semiconductor (CMOS) that can tune time delays with a phase resolution of 1 degree over an ultra-wide band of 14 GHz.

“Our design objective was to pack in as many of these delay elements as possible,” Govind said. “To route the signal, he imagined what would happen if he wrapped it around a three-dimensional waveguide and reflected the signal from it. Rather than spreading the long wavelength wire laterally across the chip, he created a delay. ”

The team designed these 3D reflectors to be strung together in a series to form a “tunable transmission line.”

The resulting integrated circuit nearly doubles the channel capacity, and therefore the data rate, of traditional wireless arrays, even though it occupies 0.13 square millimeters of space, smaller than a phase shifter. Also, by increasing predicted data speeds, the chip will be able to deliver faster service and more data to mobile phone users.

“The big problem with phased arrays is the tradeoff between making these things small enough to fit on a chip and maintaining efficiency,” Apsell said. “The answer that most of the industry has come up with is, ‘You can’t do a time delay, so you’re going to do a phase delay.’ And that fundamentally limits the amount of information you can send and receive. will only take the brunt of it.”

“I think one of our key innovations is actually asking the question, do we need to build this way?” Apsell said. “If you can increase channel capacity by a factor of 10 by changing one component, that’s a very interesting transformation for communications.”