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Recent research has helped to quantify how ICs couple to the structures on printed circuit boards that serve as antennas resulting in radiated emissions problems [7]. Most lines of electric flux emanating from an IC are captured by the circuit board or nearby metal objects and do not contribute significantly to radiated emissions below 1 GHz. On the other hand, electric field lines that escape the immediate environment of the IC/package structure induce common-mode currents on cables and chassis components. These common mode currents are generally responsible for unwanted radiated emissions. AQ,"):ofvT Recently, it was shown that hybrid TEM cell measurements are capable of quantifying the electric field coupling potential of an IC/package configuration [8]. TEM cell measurements can be used to create models that express the ability of the IC to couple to external objects. These models can replace the complex IC/package structure in full-wave system models. Thus, with a single, repeatable measurement, it is possible to capture all the relevant information about an IC/package’s ability to couple noise to external objects through an electric field. |;&I$'i MAGNETIC FIELD COUPLINGThe figure on the right illustrates an example of magnetic field coupling from an IC. In this case, the “antenna” is a cable being driven against the part of the circuit board on the opposite side of the IC. Magnetic flux generated by the IC wraps around the circuit board and generates a voltage across the board capable of driving high frequency currents onto the cable resulting in radiation. p,!IPWo The same hybrid TEM cell set-up that is used to measure electric-field coupling can be used to measure magnetic-field coupling. Generally, magnetic fields from IC/package structures cause radiated emissions problems when they wrap around other conductors (e.g. the circuit board’s ground plane) and generate a voltage across the conductor that drives common-mode currents onto cables or to other conducting objects that serve as antennas. |*M07Hc x Hybrid TEM cell measurements quantify an IC/package’s ability to couple to nearby objects in this manner. Just as an electric-field hybrid TEM cell measurement can be used to determine an “electric moment”; a magnetic-field hybrid TEM cell test can be used to determine a “magnetic moment” that can represent the IC/package in full-wave simulations [9]. v=Q!i
oE7 REFERENCES[1] IEC 61967-1 Integrated circuits - Measurement of electromagnetic emissions, 150 kHz to 1 GHz - Part 1: General conditions and definitions, International Electrotechnical Commission, Geneva, Switzerland, March 2002. 57O|e/2 [2] IEC 61967-2 Integrated circuits - Measurement of electromagnetic emissions, 150 kHz to 1 GHz - Part 2: Measurement of radiated emissions, TEM-cell and Wideband TEM-cell method, International Electrotechnical Commission, Geneva, Switzerland, Draft 47A/619/NP, October 2001. Ql9>i;AGV [3] IEC 61967-3 Integrated circuits - Measurement of electromagnetic emissions, 150 kHz to 1 GHz - Part 2: Measurement of radiated emissions, Surface scan method, International Electrotechnical Commission, Geneva, Switzer-land, Draft 47A/620/NP, October 2001. !6a;/ys [4] IEC 61967-4 Integrated circuits - Measurement of electromagnetic emissions, 150 kHz to 1 GHz - Part 4: 1Ω/150Ω direct coupling method, International Electrotechnical Commission, Geneva, Switzerland, April 2002. e+:X%a4\ [5] IEC 61967-5 Integrated circuits - Measurement of electromagnetic emissions, 150 kHz to 1 GHz - Part 5: Workbench Faraday cage method, International Electrotechnical Commission, Geneva, Switzerland, February 2003. QpRk5NeLe [6] IEC 61967-6 Integrated circuits - Measurement of electromagnetic emissions, 150 kHz to 1 GHz - Part 5: Magnetic probe method, International Electrotechnical Commission, Geneva, Switzerland, June 2002. esq~Ehr= [7] H. Shim and T. Hubing, “Model for estimating radiated emissions from a printed circuit board with attached cables driven by voltage-driven sources,”IEEE Transactions on Electromagnetic Compatibility, vol. 47, no. 4, Nov. 2005, pp. 899-907. eW8{],B [8] S. Deng, T. Hubing and D. Beetner, “Characterizing the electric-field coupling from IC-heatsink structures to external cables using TEM-cell measurements,” to appear in the IEEE Trans. on EMC, 2008. ~
wOMT [9] T. Hubing, S. Deng, and D. Beetner, “Using electric and magnetic ‘moments’ to characterize IC coupling to cables and enclosures,”Proceedings of EMC Compo 2007 Conference, Turin, Italy, November 2007
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