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64 DESIGN007 MAGAZINE I SEPTEMBER 2018 Port 1 and 3 in the same phase respectively, the forward current flows along the signal wires from board "A" to "B," whereas the return current flows along the ground wires from board "B" back to "A." The surface return cur- rent density for test case 1, 2 and 3 is 40A/m, 50A/m and 90A/m respectively. Current den- sity for case 3 almost doubles vs. the other two cases, because its sole ground wire becomes the return path bottleneck to be shared com- monly by two signal traces. Summary It is crucial to provide a continuous and suf- ficient ground or return path for signals during multi-board connection to minimize signal crosstalk. This is achievable by assigning sig- nal routing in the pattern of signal-ground- signal-ground. DESIGN007 References 1. Keysight EMPro guide. Chang Fei Yee is a hardware engineer with Keysight Technologies. His responsibilities include embedded system hardware development, and signal and power integrity analysis. Figure 6: Surface current density on ground wire for the three test cases. UC Berkeley engineers have created a device that reduces the energy needed to power magnetic field detectors. "The best magnetic sensors out there today are bulky, only operate at extreme temperatures and can cost tens of thousands of dollars," said Dominic Labanowski, a postdoctoral researcher in the Department of Electrical Engineering and Computer Science. "Our sensors could replace those more difficult-to-use sensors in a lot of applications from navigation to medical imaging to natu- ral resource exploration." Medical applications of magnetic sensors include magnetoencephalography or magnetocardiography. The sensors could also be placed in planes or drones to aid in spotting rare earth metals underground, or in cell phones. (Source: UC Berkeley) Diamond Dust Enables Low-Cost, High-Efficiency Magnetic Field Detection

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