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10 The PCB Design Magazine • October 2017 Andy Shaughnessy is managing editor of The PCB Design Magazine. He has been covering PCB design for 18 years. He can be reached by clicking here. about one aspect of signal integrity or anoth- er. New low-loss materials are constantly be- ing rolled out to help with signal integrity, and most EDA companies now offer some flavor of tool that can design high-speed, high-frequen- cy boards. As the saying goes, "If you don't have signal integrity issues now, you will." This month, we decided to delve deep into signal integrity. We kick things off with our ex- perts discussion featuring Michael Steinberger of SiSoft, Mark Thompson of Prototron Circuits, and Yogen and Sunny Patel of Candor Indus- tries, along with Happy Holden. This was one free-wheeling discussion! Learning about how fabricators and designers approach signal integ- rity challenges was a real eye-opener, to borrow a terrible pun. Next, Barry Olney of In-Circuit Design looks into exactly when a trace becomes a transmis- sion line. Admit it; you've wondered about that very point, haven't you? Bert Simonovich of Lamsim Enterprises discusses some new ways to model high-speed backplane channels. Then, Oracle's Istvan Novak explores ways to use caus- al models for your power delivery network to achieve more accurate results. Marty Gaudion of Polar Instruments brings us a feature column on loss tangent values, and he explains how to use Svensson-Djordjevic modeling to predict loss tangent and dielectric constant. John Coonrod of Rogers Corporation discusses the impact of final plated finishes on RF PCB performance. We also have a couple of interviews. Walter Katz, chief scientist for SiSoft, explains how Si- Soft is preparing for the launch of DDR5 next year, and how AMI can be used to model DDR5 data transfers. Chris Hunrath and Norm Berry of Insulectro discuss their partnership with Isola, and their desire to educate PCB designers about selecting the right low-loss material for their signal integrity needs. It's hard to believe we're winding this year up already, but we still have a lot to do. We'll be covering productronica in Munich, Germa- ny, from beginning to end, and I'm excited to be attending my first productronica. I've never been to Germany, but I do know a lot of Ger- man nouns (mainly from watching "Hogan's Heroes"). Next month we take on HDI, so don't miss out. If you aren't already a subscriber, click here to sign up now! PCBDESIGN KEEPING AN EYE ON SIGNAL INTEGRITY Using flexible conducting polymers and novel circuitry patterns printed on paper, researchers have demonstrated proof-of-concept wearable thermoelectric generators that can harvest energy from body heat to power simple biosensors for measuring heart rate, respiration or other factors. "The attraction of thermoelectric generators is that there is heat all around us," said Akanksha Menon, a Ph.D. student in the Woodruff School of Mechanical Engineering at the Georgia Institute of Technology. "If we can harness a little bit of that heat and turn it into electricity inexpensively, there is great value." To overcome that, Menon and collaborators in the laboratory of Assistant Professor Shannon Yee designed a device with thousands of dots com - posed of alternating p-type and n-type polymers in a closely-packed layout. By placing the polymer dots closer together, the interconnect length decreases, which in turn lowers the total resistance and results in a higher power output from the device. The new circuit design also has another benefit: its fractally symmetric design allows the modules to be cut along boundaries between symmetric areas to provide exactly the voltage and power needed for a specific application. That eliminates the need for power converters that add complexity and take power away from the system. Novel Circuit Design Boosts Wearable Thermoelectric Generators