Researchers at Columbia University’s Fu Foundation School of Engineering and Applied Science are the first to demonstrate a circulator on a silicon chip at millimeter-wave frequencies, enabling nonreciprocal transmission of waves.
Paving the way for new two-way radios, 5G networks, self-driving cars and enhanced virtual reality, the researchers led by Harish Krishnaswamy, an associate professor of electrical engineering at Columbia collaborated with researchers from the University of Texas–Austin led by Andrea Alu, professor in electrical and computer engineering and holder of the Temple Foundation Endowed Professorship No. 3.
Typical devices operate in a reciprocal manner – signals travel in the same manner in forward and reverse. However, nonreciprocal devices, such as circulators allow those signals to travel on different separate paths. These devices are built from magnetic materials, making them bulky, expensive and generally not suitable for consumer wireless electronics.
Solving these issues, the team developed a new way of enabling nonreciprocal transmission of waves, using carefully synchronized high-speed transistor switches that route forward and reverse waves in different manners. Notably, this approach enables circulators to be built in conventional semiconductor chips and operate at millimeter-wave frequencies. Whereas most electronic devices operate at overused sub-6 GHz frequencies, these circulators enable higher millimeter waves frequencies of 30 GHz and above, opening up new bandwidth that is not currently in use.
“This gives us a lot more real estate,” notes Krishnaswamy. “This mm-wave circulator enables mm-wave wireless full-duplex communications, and this could revolutionize emerging 5G cellular networks, wireless links for virtual reality, and automotive radar.”
To learn more about this project, click here.