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36 The PCB Design Magazine • January 2016 Points to Remember: • Tight coupling between adjacent planes can be utilized to add planar capacitance and dramatically reduce the AC imped- ance at the high end. • Planar capacitor laminate, also known as embedded capacitor material, is becom- ing a cost-effective solution to further im- proved power integrity. • Solid power and ground planes encompass a distributed system of surprising com- plexity. • A distributed system involves the relation- ship between the time delay of the system and the rise-time of the signals. • During the rising and falling edge, the lo- cal planes and decaps cannot react before the edge has vanished. This frequently re- sults in a large noise spike. • Repetitive pulse clocks tend to superim- pose and build significant peaks. • Avoid potential failure by comparing the round-trip delay across the plane, to the clock period. • A "rough wave" is formed when a long, slow oscillation is followed by a short and fast oscillation. • A combination of modifications to dielec- tric thickness and dielectric constant of the material in the ICD Stackup Planner, together with an adjustment of plane size, can usually establish the minimum reso- nance for the configuration. PCBDESIgN References 1. Barry Olney's Beyond Design columns: No One-Way Trips, The Dumping Ground, Los- ing a Bit of Memory, Stackup Planning Parts 1-4, Material Selection for SERDES Design. 2. Henry Ott: Electromagnetic Compatibil- ity Engineering 3. Howard Johnson: High-speed Signal Prop- agation 4. Masanori Hashimoto and Raj Nair: Power Integrity for Nanoscale Integrated Systems 5. The ICD Stackup and PDN Planner: www. Barry olney is managing director of In-Circuit Design Pty ltd (ICD), Australia. This PCB design service bureau specializes in board-level simulation, and has developed the ICD Stackup Planner and ICD PDn Planner software. To read past columns, or to contact olney, click here. nanotechnologists at the university of Twente research institute MeSA+ have discovered a new fundamental property of electrical currents in very small metal circuits. They show how electrons can spread out over the circuit like waves and cause in- terference effects at places where no electrical cur- rent is driven. The geometry of the circuit plays a key role in this so called nonlo- cal effect. For designers of quantum computers it is an ef- fect to take account of. Interference is a common phenomenon in nature and oc- curs when one or more propa- gating waves interact coherently. Interference of sound, light or water waves is well known, but also the carriers of electrical current—electrons—can in- terfere. It shows that electrons need to be consid- ered as waves as well, at least in nanoscale circuits at extremely low temperatures. The researchers have demonstrated electron in- terference in a gold ring with a diameter of only 500 nanometers. one side of the ring was connected to a miniature wire through which an electrical cur- rent can be driven. on the other side, the ring was connected to a wire with a voltmeter attached to it. now the researchers have discovered a new way to af- fect the dynamical nonlocali- ty. understanding this funda- mental effect is important for future quantum information processing. Spooky Interference at a Distance beyond design PLANE CRAzY, PART 2

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