Researchers demonstrate a circulator on a silicon chip at mm-wave frequencies: Page 2 of 3

October 09, 2017 //By Jean-Pierre Joosting
Researchers from Columbia Engineering, led by Harish Krishnaswamy, associate professor of electrical engineering, in collaboration with Professor Andrea Alu's group from UT-Austin, claim to be the first to demonstrate a circulator on a silicon chip at mm-wave frequencies that enables nonreciprocal transmission of waves: device could enable two-way radios and transform 5G networks, self-driving cars, and virtual reality.

This new approach enables circulators to be built in conventional semiconductor chips and operate at millimeter-wave frequencies, enabling full-duplex or two-way wireless. Virtually all electronic devices currently operate in half-duplex mode at lower radio-frequencies (below 6 GHz), and consequently, we are rapidly running out of bandwidth. Full-duplex communications, in which a transmitter and a receiver of a transceiver operate simultaneously on the same frequency channel, enables doubling of data capacity within existing bandwidth. Going to the higher mm-wave frequencies, 30 GHz and above, opens up new bandwidth that is not currently in use.

"This gives us a lot more real estate," notes Krishnaswamy, whose Columbia High-Speed and Mm-wave IC (CoSMIC) Lab has been working on silicon radio chips for full duplex communications for several years. His method enables loss-free, compact, and extremely broadband non-reciprocal behavior, theoretically from DC to daylight, that can be used to build a wide range of non-reciprocal components such as isolators, gyrators, and circulators.

"This mm-wave circulator enables mm-wave wireless full-duplex communications, Krishnaswamy adds, "and this could revolutionize emerging 5G cellular networks, wireless links for virtual reality, and automotive radar."

Self-driving cars, for instance, require low-cost fully-integrated millimeter-wave radars. These radars inherently need to be full-duplex, and would work alongside ultra-sound and camera-based sensors in self-driving cars because they can work in all weather conditions and during both night and day. The Columbia Engineering circulator could also be used to build millimeter-wave full-duplex wireless links for VR headsets, which currently rely on a wired connection or tether to the computing device.