Cornell engineers develop cancellation technique for range of frequencies

Researchers at Cornell have devised a method for transmitting and receiving a radio signal on a single chip.

Researchers at a Cornell University lab say they have devised a method for both transmitting and receiving a radio signal on a single chip—one that can work over a range of frequencies.

The work by Alyosha Molnar, associate professor of electrical and computer engineering (ECE) at Cornell, and Alyssa Apsel, professor of ECE, and team is described in “A wideband fully integrated software-defined transceiver for FDD and TDD operation,” published online Jan. 27 in the Institute of Electrical and Electronics Engineers’ Journal of Solid-State Circuits.

As the Cornell Chronicle notes, separating the send and receive is difficult enough, but the problem is compounded by the ever-increasing number of bands in devices. From GPS to Bluetooth to Wi-Fi, each requires a filter to stop strong transmit signals from drowning out reception.

The Cornell team’s idea lies in the transmitter—actually, a series of six subtransmitters hooked into an artificial transmission line. Each sends its signal at regular intervals, and their individually weighted outputs are programmed so that they combine to produce a radio frequency signal in the forward direction, at the antenna port, while canceling out at the receive port.

Instead of needing a filter for every band, signal separation can be controlled digitally. Upgrading to the latest version would be like updating an app—as simple as downloading the latest software. “You could have a single device that can be anything,” Apsel told the Chronicle. “You wouldn’t have to buy a new piece of equipment to have the newest version of it.”

The concept builds off of full-duplex work conducted by students at Stanford University, but unlike the Stanford work, the Cornell group’s subtransmitter concept will work over a range of frequencies, the Chronicle reports. “This wire is a fairly broadband structure,” Molnar said. “And the thing you do to make it work over a wide range of frequencies is just control those different subgains of the transmitters, to make this cancellation always happen.”

Other researchers also have produced breakthroughs over the years in the full-duplex space, but Kumu Networks—which was founded by the students at Stanford—has been developing a product for commercial use. Kumu Networks is working with a carrier in Europe to deploy its first generally available product and expects to sell products in “relatively reasonable quantities" this year, co-founder Steven Hong told FierceWirelessTech.

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At a high level, Kumu has been developing a self-interference technology that allows a radio to completely silence its own transmission, such that it can receive in the same band. The long-term application is to double the spectral efficiency of all the users, but the intermediate effect is where it has developed the product initially: in the full-duplex relay application.

Kumu also has been exploring a new architecture where cancellation technology is deployed only in the base station and it’s able to achieve full duplex without deploying the cancellation at the handset. It’s not quite small enough yet to go into smartphones, but a lot of operators are interested in the development.