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New Method Uses CMOS Technology to Improve High-Bandwidth Communications over Extremely Long Distances

News — New York, NY鈥擜pril 24, 2013鈥擧arish Krishnaswamy, assistant professor of electrical engineering at Columbia Engineering, has generated a record amount of power output鈥攂y a power of five鈥攗sing silicon-based nanoscale CMOS (complementary metal oxide semiconductor) technology for millimeter-wave power amplifiers. Power amplifiers are used in communications and sensor systems to boost power levels for reliable transmission of signals over long distances as required by the given application. Krishnaswamy鈥檚 research will be reported at the June 2013 Institute of Electrical and Electronics Engineers Radio Frequency Integrated Circuits Symposium.

Used in virtually all forms of electronics around us, from phones to PCs, laptops, and tablets to satellite communications, nanoscale CMOS technologies have enabled the digital and communication revolution over the past 20 to 30 years. While nanoscale CMOS can do many things, Krishnaswamy explains the one thing that it cannot do very well is generate large amounts of power at high frequencies. This is because as transistors become smaller, they tend to break very easily with even a small amount of voltage or current鈥斺�渢hey鈥檙e great for speed, but not power,鈥� he notes. But generating large amounts of power at high frequencies is critical for communication over large distances with high bandwidth.

鈥淲e have devised a way to use multiple nanoscale CMOS transistors in carefully-aligned synchrony to 鈥榮hare the load鈥� and generate nearly a watt of power at millimeter-wave frequencies鈥攏early five times greater than what was currently possible,鈥� says Krishnaswamy. 鈥淭his could enable extremely high-bandwidth communication over extremely long distances for the first time.鈥�

For instance, he points out, think of a citywide millimeter-wave wireless network that could support 10s of gigabit per second data rates鈥攏early two to three orders of magnitude higher than WiFi. Such a network could serve as the backbone infrastructure that enables extremely high-data-rate wireless links to mobile devices.

Krishnaswamy and his CoSMIC lab team accomplished this world record power output level for CMOS-based power amplifiers by developing a chip design methodology that stacks several nanoscale CMOS devices on top of each other so that they can handle larger voltages without compromising their speed. By stacking four 45 nanometer CMOS transistors within a power amplifier and then combining eight such amplifiers on a single chip, they achieved output power levels of nearly 0.5 W at 45 gigahertz.

鈥淗igh-frequency nanoscale electronics is exciting to me because it is the confluence of many different aspects of science and engineering,鈥� Krishnaswamy observes. 鈥淚t鈥檚 an area where theory meets experimentation, where electro-magnetics meets chip and circuit design, and where the abstract meets real-life applications. I find it fascinating.鈥�

The research was funded by DARPA MTO (Defense Advanced Research Projects Agency鈥檚 Microsystems Technology Office) through its ELASTx (Efficient Linearized All-Silicon Transmitter ICs) program.

Columbia EngineeringColumbia University's Fu Foundation School of Engineering and Applied Science, founded in 1864, offers programs in nine departments to both undergraduate and graduate students. With facilities specifically designed and equipped to meet the laboratory and research needs of faculty and students, Columbia Engineering is home to NSF-NIH funded centers in genomic science, molecular nanostructures, materials science, and energy, as well as one of the world鈥檚 leading programs in financial engineering. These interdisciplinary centers are leading the way in their respective fields while individual groups of engineers and scientists collaborate to solve some of modern society鈥檚 more difficult challenges. http://www.engineering.columbia.edu/

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