On-chip RF circulator and a single antenna to double Wi-Fi speed

April 22, 2016 // By Jean-Pierre Joosting
Full-duplex radio ICs that can be implemented in nanoscale CMOS to enable simultaneous transmission and reception at the same frequency in a wireless radio were first invented last year by Columbia Engineering researchers. That system required two antennas, one for the transmitter and one for the receiver. Now the team, led by Electrical Engineering Associate Professor Harish Krishnaswamy, has developed a breakthrough technology that needs only one antenna, thus enabling an even smaller overall system.

This is the first time researchers have integrated a non-reciprocal circulator and a full-duplex radio on a nanoscale silicon chip.

"This technology could revolutionize the field of telecommunications," says Krishnaswamy, director of the Columbia High-Speed and Mm-wave IC (CoSMIC) Lab. "Our circulator is the first to be put on a silicon chip, and we get literally orders of magnitude better performance than prior work. Full-duplex communications, where the transmitter and the receiver operate at the same time and at the same frequency, has become a critical research area and now we've shown that Wi-Fi capacity can be doubled on a nanoscale silicon chip with a single antenna. This has enormous implications for devices like smartphones and tablets."

Krishnaswamy's group has been working on silicon radio chips for full duplex communications for several years and became particularly interested in the role of the circulator, a component that enables full-duplex communications where the transmitter and the receiver share the same antenna. In order to do this, the circulator has to "break" Lorentz Reciprocity, a fundamental physical characteristic of most electronic structures that requires electromagnetic waves travel in the same manner in forward and reverse directions.

This is the first CMOS full duplex receiver IC with integrated magnetic-free circulator. Image courtesy of Negar Reiskarimian, Columbia Engineering.