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22 The PCB Design Magazine • September 2016 press) that are spliced together. Another very large flex I did was a phased array antenna that was designed to deploy on an inflatable frame on orbit. Another large flex circuit design was a pro- totype heater for HP. It wasn't huge, but it was jam-packed with eight heater zones and over .23 miles of conductors. The goal on this design was to maximize distribution, and then adjust the trace width for the desired resistance. My most interesting flex design was probably a rigid-flex I did for Panavision. The center seg- ment supported the CCD sensor, and four legs folded down, enveloping the lens stack to sup- port the other electronics. Or it may have been some circular phased patch array antennas I did at JPL. These were about 3m in diameter and were filled with tuned RF elements on about a 1/4" grid. Each element was "tuned" by adjusting the length of the two RF stubs that came out of it. Each element's stub length depended on its loca - tion on the array. I designed these with Comput- ervision Cadds4 by constructing an executable file that placed polygons at each location based on an input file from the antenna engineer. It doesn't sound interesting, but when it was done, you could discover some beautiful patterns. Shaughnessy: I understand that you may have de- signed the first flex ever used at JPL. Can you tell us about that? Cardone: I am not certain this was the first use of flex at JPL. It is the first one I was aware of. For the Cassini mission we designed a flex that adapted a sub-d connector to surface mount interface at the PWB. Its construction was a 3 oz. layer of Cu or BeCu sandwiched between polyimide layers. The connector interface was through-hole, and the PWB interface was un- supported flying leads of the BeCu that exited the sandwich. The flex exited the connector pin array in both directions to allow maximum trace width, and keep the flex to one layer. The flex leg near the PWB had a 90 degree turn, the leg away from the PWB had a 180, and then a 90 degree turn. The end result was that we only took up about .55" of PWB area, while a round wire interface might have taken twice that. Shaughnessy: Thanks for talking with us, John. Cardone: Thank you. PCBDESIGN Applied scientists led by Caltech's Kerry Va- hala have discovered a new type of optical soli- ton wave that travels in the wake of other soliton waves, hitching a ride on and feeding off of the en- ergy of the other wave. Solitons are localized waves that act like parti- cles: as they travel across space, they hold their shape and form rather than dispersing as other waves do. They were first discovered in 1834 when Scottish engineer John Scott Russell noted an un- usual wave that formed after the sudden stop of a barge in the Union Canal that runs between Falkirk and Edinburgh. Russell tracked the result- ing wave for one or two miles, and noted that it preserved its shape as it traveled, until he ulti- mately lost sight of it. The microcavities that Vahala and his team use include a laser input that provides the solitons with energy. This energy can- not be directly absorbed by the Stokes soliton—the "pilot fish." Instead, the energy is consumed by the "shark" soliton. But then, Vahala and his team found, the energy is pulled away by the pilot fish soliton, which grows in size while the other soliton shrinks. New Breed of Optical Soliton Wave Discovered JOHN CARDONE ON DESIGNING FLEX FOR SPACECRAFT

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