The PCB Design Magazine

PCBD-Oct2017

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October 2017 • The PCB Design Magazine 19 "And anybody can veto a standard and keep it from being published, until you water it down, until you finally get a consensus," added Holden. "The problem with most of the standards is that they have been designed in early days," Yo- gen said. "And then nobody wants to challenge history again." So, everyone agreed that signal integrity isn't just a problem for PCB designers and design engineers; today's high-speed, high-frequency boards with can wreak havoc downstream. It was an eye-opening conversation for everyone involved. Steinberger summed it up: "One thing I can promise you is that, from this discussion, there are a couple of col- leagues that I will ask about landless vias just to see what they know," said Steinberger. "Be- cause I am working with some people who are actively designing a system at 28 gigabits and starting to plan for 56 gigabits, and it would be interesting to see what those people have to say." PCBDESIGN "Yeah, you won't get any at all," replied Holden. "Which is why HP and IBM ignored IPC standards, because they made our competi- tors less competitive. And we knew it was all propaganda. They didn't have any data to sup- port any kind of use of lands, but we had data, and we traded it with IBM. They had the same data." Steinberger said the standardization process itself is partly to blame for such impasses. "I do observe that, for those who have not been in- volved in a standardization process, they think that standards are extremely intelligent and ex- tremely reliable. For those of us who have been deeply involved in the standards process, we know otherwise. Part of the problem with the standardization process is that not everybody in the committee has the same goal. So although you can get an informed debate, and there are some standards bodies in which people are re- sponsible, the fact of the matter is that if people don't have the same goal, then what you get is not necessarily going to serve any one goal very well." SIGNAL INTEGRITY: THE EXPERTS WEIGH IN Columbia Engineering researchers, led by Harish Krishnaswamy, associate professor of electrical engineering, in collaboration with Professor Andrea Alu's group from UT-Austin, continue to break new ground in developing magnet-free non-reciprocal compo- nents in modern semiconductor processes. At the IEEE International Solid-State Circuits Conference in February, Krishnaswamy's group unveiled a new de- vice: the first magnet-free non-reciprocal circulator on a silicon chip that operates at millimeter-wave fre- quencies (frequencies near and above 30GHz). Most devices are reciprocal: signals travel in the same manner in forward and reverse direc- tions. Nonreciprocal devices, such as circulators, on the other hand, allow forward and reverse sig- nals to traverse different paths and therefore be separated. Traditionally, nonreciprocal devices have been built from special magnetic materials that make them bulky, expensive, and not suitable for consumer wireless electronics. The team has developed a new way to enable nonreciprocal trans- mission of waves: using carefully synchronized high-speed transis- tor switches that route forward and reverse waves differently. In effect, it is similar to two trains approaching each other at super-high speeds that are detoured at the last moment so that they do not collide. The implications are enormous. 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-driv- ing cars because they can work in all weather con- ditions and during both night and day. The Co- lumbia 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. Researchers Invent Breakthrough Millimeter-wave Circulator IC

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