GALLIUM NITRIDE VACUUM TUBES GREENHOUSE-GAS HOW LOW CAN GETS READY FOR 6G OF THE COLD WAR SENSING SATELLITES LATENCY GO? Jump in efficiency Nine wild devices Microsatellites spot Wireless researchers astounds experts you’ve never heard of methane—for a profit push the limits P. 07 P. 30 P. 38 P. 44 FOR THE TECHNOLOGY INSIDER | 11.20 The Incredible BENDABLE Smartphone Foldable phones are just the beginning— stretchable, wearable displays are already in the laboratory P. 24 Keep pushing the limits! Congratulations to Peter Grutter and his group at the Nanoscience & SPM Lab at McGill University on bridging the gap between high spatial and ultrafast temporal resolution to advance molecular and quantum electronics. Observing 100 fs non-linear Megan Cowie, Nanoscience & SPM Group, optical interactions and quantized vibration-modified McGill University electron transfer in single molecules with AFM are impressive achievements that set new standards at the forefront of scientific research. We are excited to continue our collaboration and look forward to finding new ways of using lock-in amplifiers and boxcar averagers to push the limits of SPM applications. Zurich www.zhinst.com Instruments Your Application. Measured. CONTENTS_11.20 30 THE 9 GREATEST 38 MICRO- 44 BREAKING 06 NEWS DISPLAYS VACUUM TUBES SATELLITES SPOT THE MILLISECOND 16 HANDS ON YOU’VE NEVER MYSTERY METHANE BARRIER It will take 20 CROSSTALK HEARD OF These LEAKS Keeping a lot of tricks to push 52 PAST FORWARD THAT BEND tubes excel where carbon-capping network latencies solid-state devices schemes on track below 1 millisecond. fall short. needs tech that can go By Shivendra Panwar AND STRETCH By Carter M. anywhere. Armstrong By Jason McKeever, Here’s how engineers are making Dylan Jervis & displays that are amazingly flexible. Mathias Strupler by Huanyu ZHao & Tae-woo Lee Page 24 On the cover and this page Conceptual photograph for IEEE Spectrum by Dan Saelinger IEEE SPECTRUM (ISSN 0018-9235) is published monthly by The Institute of Electrical and Electronics Engineers, Inc. All rights reserved. © 2020 by The Institute of Electrical and Electronics Engineers, Inc., 3 Park Avenue, New York, NY 10016-5997, U.S.A. Volume No. 57, Issue No. 11. The editorial content of IEEE Spectrum magazine does not represent official positions of the IEEE or its organizational units. Canadian Post International Publications Mail (Canadian Distribution) Sales Agreement No. 40013087. Return undeliverable Canadian addresses to: Circulation Department, IEEE Spectrum, Box 1051, Fort Erie, ON L2A 6C7. Cable address: ITRIPLEE. Fax: +1 212 419 7570. INTERNET: [email protected]. ANNUAL SUBSCRIPTIONS: IEEE Members: $49.95 included in dues. Libraries/institutions: $399. POSTMASTER: Please send address changes to IEEE Spectrum, c/o Coding Department, IEEE Service Center, 445 Hoes Lane, Box 1331, Piscataway, NJ 08855. Periodicals postage paid at New York, NY, and additional mailing offices. Canadian GST #125634188. Printed at 120 Donnelley Dr., Glasgow, KY 42141-1060, U.S.A. IEEE Spectrum circulation is audited by BPA Worldwide. IEEE Spectrum is a member of the Association of Business Information & Media Companies, the Association of Magazine Media, and Association Media & Publishing. IEEE prohibits discrimination, harassment, and bullying. For more information, visit https://www.ieee.org/web/aboutus/whatis/policies/p9-26.html. SPECTRUM.IEEE.ORG | NOV 2020 | 01 BACK STORY LIFE OF A TUBE GUY Increased Performance for Connected Hardware f you’d told me I’d spend my career working on vacuum tubes, I’d have said, ‘No way. That’s crazy!’ ” So says Carter M. Armstrong, who has in fact spent the last Designed to perform in 40-some years working on vacuum devices. It started in graduate high vibration environments school, when his Ph.D. advisor at the University of Maryland turned him on to electron beams. And it continued through With surface mount solder tabs for stints at North Carolina State University, the Naval Research additional board retention strength, I Laboratory, Northrop Grumman, Litton, and most recently Archer Kontrol can withstand L3Harris, in Torrance, Calif., where he is director of advanced lateral and twisting forces in high development for the company’s Electron Devices division. vibration environments. Throughout, Armstrong says, the work has been intellectually stimulating and emotionally rewarding. “It’s good to work on hard Ensuring reliability in the problems,” he says. “The physics is hard, the engineering is hard, next generation of connected and it’s all interrelated. Not everybody can do this kind of work, but devices. it gets in your blood, it really does.” n Temperature range of In the photo above, Armstrong, an IEEE Fellow, holds two of -55°C to +125°C the devices he helped develop: a millimeter-wave mini traveling- n Assists with blind mating wave tube and a microwave power module, both of which he describes in “The 9 Greatest Vacuum Tubes You’ve Never Heard n Tested to perform up to Of” [p. 30]. Beyond the ubiquitous magnetrons in microwave ovens 500 operations and the traveling-wave tubes in communications satellites, he says, n Up to 3 Gbit/s data rate vacuum devices still find their way into a surprisingly broad array of applications where “you need high efficiency, high power, and wide amplification bandwidth.” Those applications include cancer harwin.com/archer-kontrol therapy, fusion reactors, industrial heating, particle accelerators, radar, missile defense, and electronic warfare. Almost all of the tubes in Armstrong’s article are ones he helped design or came across during his career, but he included one based on the recommendation of his son Derek, a musician. That’s the Telefunken VF14M, a specialized audio tube used in the much- Connect with confidence revered Neumann U47 and U48 microphones. Over the decades, many recording artists have favored those mics, including Ella Fitzgerald, Frank Sinatra, and the Beatles. 11.20 “I’m a huge Beatles fan, so I was more than happy to include that one,” Armstrong says. ■ MARTIN MICHAEL 02 | NOV 2020 | SPECTRUM.IEEE.ORG Harwin Archer Kontrol IEEE Spectrum Sept 20.indd 1 03/08/2020 09:45 CONTRIBUTORSCONTRIBUTORS_ EDITOR IN CHIEF Susan Hassler, [email protected] ADVERTISING PRODUCTION +1 732 562 6334 EXECUTIVE EDITOR Glenn Zorpette, [email protected] ADVERTISING PRODUCTION MANAGER EDITORIAL DIRECTOR, DIGITAL Felicia Spagnoli, [email protected] Daniel P. Dern SENIOR ADVERTISING PRODUCTION COORDINATOR Harry Goldstein, [email protected] Dern is a veteran technology and business writer MANAGING EDITOR Elizabeth A. Bretz, [email protected] Nicole Evans Gyimah, [email protected] based in Boston. He also pens science fiction SENIOR ART DIRECTOR EDITORIAL ADVISORY BOARD, IEEE SPECTRUM and is an amateur magician. For this issue, Dern Mark Montgomery, [email protected] Susan Hassler, Chair; David C. Brock, Ronald F. DeMara, interviewed Merryl Gross about designing user SENIOR EDITORS Shahin Farshchi, Lawrence O. Hall, Jason K. Hui, experiences (UX) [p. 19]. Although he and Gross Stephen Cass, [email protected] Leah Jamieson, Mary Lou Jepsen, Deepa Kundur, have known each other for decades and attend the Erico Guizzo (Digital), [email protected] Gianluca Lazzi, Allison Marsh, Carmen Menoni, Sofia Olhede, Jean Kumagai, [email protected] Maurizio Vecchione, Edward Zyszkowski same sci-fi conferences, he says, “I hadn’t had the Samuel K. Moore, [email protected] chance to learn what she does as an information EDITORIAL ADVISORY BOARD, THE INSTITUTE Tekla S. Perry, [email protected] architect, and what UX is all about. I love talking Kathy Pretz, Chair; Qusi Alqarqaz, Philip Chen, Roberto Graglia, Philip E. Ross, [email protected] with people about how they got into their fields.” Shashank Gaur, Susan Hassler, Cecilia Metra, San Murugesan, David Schneider, [email protected] Mirela Sechi Annoni Notare, Tapan K. Sarkar, Joel Trussell, Eliza Strickland, [email protected] Hon K. Tsang, Chonggang Wang DEPUTY ART DIRECTOR Brandon Palacio, [email protected] MANAGING DIRECTOR, PUBLICATIONS Steven Heffner PHOTOGRAPHY DIRECTOR Randi Klett, [email protected] Jason McKeever ONLINE ART DIRECTOR Erik Vrielink, [email protected] EDITORIAL CORRESPONDENCE McKeever is the science and systems lead at GHGSat, ASSOCIATE EDITORS IEEE Spectrum, 3 Park Ave., 17th Floor, Willie D. 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