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October 2016 • The PCB Design Magazine 63 physical features of woven glass can have di- mensions which are 1/8 wavelength or larger at millimeter-wave frequencies. One issue is so- called "glass knuckles," which occurs when the different strands of the glass weave overlay and these knuckles have a concentration of glass. The glass is usually a much different Dk than the resin system and this difference, combined with the dimensions of areas of glass (knuckles) and no-glass (open areas between knuckles), can be a major issue for signal integrity. There are several ways to deal with the glass weave issue and a simple one is to put the circuit conductor runs on an angle related to the glass weave pat- tern. This angle helps average the effect of the glass weave. Also, materials using a spread-glass or flat-glass can be used to help minimize differ- ences in glass weave effect. This column very quickly touches on a vast topic, so it is highly recommended that the PCB designer contact their material supplier to understand the different material issues when dealing with HSD designs as well as millimeter- wave applications. PCBDESIGN John Coonrod is the technical mar- keting manager at Rogers Corpora- tion. To contact him, click here. With the high en- vironmental cost of conventional energy sources and the finite supply of fossil fuels, the importance of renew- able energy sources has become much more ap- parent in recent years. However, efficiently harnessing solar energy for human use has been a difficult task. While silicon-based solar cells can be used to capture sunlight energy, they are costly to produce on an industrial scale. Research from the Energy Materi- als and Surface Sciences Unit at the Okinawa Insti- tute of Science and Technology Graduate Univer- sity (OIST), led by Prof. Yabing Qi, has focused on using organo-metal halide perovskite films in solar cells. These perovskite films are highly crystalline materials that can be formed by a large number of different chemical combinations and can be de- posited at low cost. In order to be useful as solar cells, perovskite films must be able to harvest solar energy at a high efficiency that is cost-effective, be relatively easy to manufacture, and be able to withstand the out- door environment over a long period of time. Dr. Yan Jiang in Prof. Qi's lab has recently pub- lished research in Mate- rials Horizons that may help increase the solar efficiency of the organo- metal halide perovskite MAPbI3. He discovered that the use of a methyl- amine solution during post-annealing led to a decrease in problems associated with grain boundaries. Grain boundaries manifest as gaps between crystalline domains and can lead to un- wanted charge recombination. This is a common occurrence in perovskite films and can reduce their efficiency, making the improvement of grain boundary issues essential to maintain high device performance. Research from Prof. Qi's research unit has brought perovskite solar cells one step closer to mass production by providing solutions to prob- lems of efficiency, life-span, and scalability. With more exciting research on the horizon, the unit is bringing the dream of utilizing cost-effective re- newable energy resources into reality. New Advances in Solar Cell Technology THE BLENDING OF HIGH-SPEED DIGITAL AND HIGH-FREQUENCY RF

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