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FEBRUARY 2020 I DESIGN007 MAGAZINE 19 Holden: If the pitch is too small, the anti-pads on the power ground layers take away all the cop- per that's required. You have noise issues and voltage drop issues underneath the BGA that will create additional headaches and problems. Ritchey: This part had 2,000 pins. The planes look a little bit like a screen, there are so many holes. This is still power delivery, but that's not where EMI comes from. The product won't work if you don't get that part right. Matties: It's all connected. Is there anything else that we should understand about this top- ic before we move forward? Ritchey: I don't think it's a complicated prob- lem, personally. The thing is that there's so much misinformation out there that the ad- vice people are given creates problems. Hav- ing been doing this for a while, I know what the problem is and that it's simple to solve, but the issue is wading through the misinformation. I would suggest that anyone who is starting out in this area read the book Principles of Power Integrity for PDN Design: Robust and Cost-Effective Designs for High- Speed Digital Products written by Larry Smith and Eric Bogatin. I would suggest that you tear up every book that claims to give you good advice on EMI (laughs). Universally, they're all wrong. Matties: Lee, thank you very much. Holden: We appreciate it. Ritchey: Thanks. DESIGN007 We've heard it for years: 5G is coming. And yet, while high-speed 5G internet has indeed slowly been rolling out in a smattering of countries across the globe, many barriers remain that have prevented widespread adoption. Researchers from MIT's Computer Science and Artificial Intelligence Laboratory (CSAIL) wondered if people have had things completely backward this whole time. Rather than focusing on the transmitters and receivers, what if they could amplify the signal by adding antennas to an external surface in the environment itself? That's the idea behind the CSAIL team's new system RFocus, a software-controlled "smart surface" that uses more than 3,000 antennas to maximize the strength of the signal at the receiver. While the system could serve as another form of the WiFi range extender, the research- ers say its most valuable use could be in the network- connected homes and factories of the future. For example, imagine a warehouse with hundreds of sensors for monitoring machines and inventory. MIT Pro- fessor Hari Balakrishnan says that systems for that type of scale would normally be prohibitively expensive and/ or power-intensive but could be possible with a low- power interconnected system that uses an approach like RFocus. "The core goal here was to explore whether we can use elements in the environment and arrange them to direct the signal in a way that we can actually control," says Balakrishnan, senior author on a new paper about RFocus that will be presented next month at the USENIX Sympo- sium on Networked Systems Design and Implementation (NSDI) in Santa Clara, California. RFocus is a two-dimensional surface composed of thousands of antennas that can each either let the signal through or reflect it. The state of the elements is set by a software controller that the team developed with the goal of maximizing the signal strength at a receiver. (Source: MIT) A Smart Surface for Smart Devices

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