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IEEE Dallas EMC Society David Johns System Level EMC Simulation Using the TLM Method.

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Presentation on theme: "IEEE Dallas EMC Society David Johns System Level EMC Simulation Using the TLM Method."— Presentation transcript:

1 IEEE Dallas EMC Society David Johns System Level EMC Simulation Using the TLM Method

2 What is FLO/EMC…? sThe first electromagnetic field simulator developed specifically for system-level EMC design in the electronics industry sEnables EMC problems to be identified and managed in the early stages of design sGood for investigating radiated & conducted emissions, immunity (susceptibility), ESD and crosstalk problems: sEnclosures & EMI shields sInterfaces between boards and chassis sCables and EMI filters sUnintentional antennas! (heat sinks etc.) sBased on the 3D Transmission-Line Matrix (TLM) Method

3 TLM Method s3D space-volume divided into nodes (10 th wavelength) sEach node is a 12-port transmission-line junction sScattering at the nodes models coupling between E and H fields sTransient E and H fields are calculated from combinations of voltages and currents on the transmission lines sSpectrum found by FFT V8 V9 V11 V10 V4 V2 V3 V6 V12 V7 V1 V5 X Y Z E y = ½ (V 3 i + V 4 i + V 8 i + V 11 i ) / Y

4 TLM Coupling Matrix YXZYXYZXYZXZYZZXZYXZXYYX 123456789101112 YX1111 ZY2111 XY3111 ZX4111 YZ5111 XZ6111 YZ7111 ZX8111 ZY9111 XZ10111 XY11111 YX12111 S = ½ Reflected Pulses V r k+1 Incident Pulses V i k E y = ½ (V 3 i + V 4 i + V 8 i + V 11 i ) / w

5 Wave Propagation, Time 0 1 1 1 1

6 Wave Propagation, Time 1 -0.5 0.5

7 Wave Propagation, Time 2 -0.5 0.5 0.25 0.5 0.25 0.5 0.25 0.5 0.25 -0.25 0.25 -0.25 0.25 -0.25 0.25 -0.25 0.25 0.5

8 Wave Propagation, Time 3

9 Complexity of EMC Analysis Compact vent model seams air vents sAccurate modeling requires geometric detail sA long narrow seam may be a good antenna! sMeshing the detail is computationally impractical connectors

10 FLO/EMC Smart Parts sTLM method uses a TL-Matrix to model fields. sOther TLs & lumped-circuit models can be connected into the matrix. s Arrays of small holes are often necessary to provide adequate thermal ventilation/cooling. s Apertures increase emissions and decrease shielding effectiveness of the box. s Low-frequency fields are evanescent near the apertures. s Extremely fine grid would be required to model the exponential decay. s FLO/EMC overcomes this difficulty by inserting a smart part into the grid.

11 Air vent smart part L models the current flow along the edges of the apertures C models the electric field stored inside the apertures. For a thin panel TEM transmission can be modelled by a shunt inductor. L is like a short at DC, but allows high freq. transmission. For a thick panel the additional electric field inside the aperture can be modelled by a shunt capacitor TEM

12 Transmission dependence on aperture shape and size, coverage and depth – empirical results Fine TLM mesh of single aperture used to calculate dependence of Transmission on aperture shape and size, coverage and depth Fit L,C air vent parameters to the Transmission results at two frequencies - 10% and 80% of aperture cut-off frequency

13 Air Vent Implementation Inductor modelled by short-circuit transmission line Capacitor modelled by open-circuit transmission line

14 1D propagation through an array of circular apertures (depth equal to diameter) Validation - Plane Wave The fine TLM mesh and air vent model give the same results at 10% and 80% of aperture cut-off frequency

15 Validation - Emission a = 50 mm b = 20 mm c = 40 mm d = 10 mm r = 10.0 mm p = 5.0 mm t = 1.65 mm N = 252 [M.Li et al,EMI…,IEEE Trans EMC, Vol. 42, No. 3, p265,2000]

16 Run time on Dual Pentium Xeon with 3 GHz clock rate Air vent model 3 min

17 Enclosure with thick walls a = 100 mm b = 80 mm c = 15 mm r = 5.08 mm p = 0.69 mm t = 5.20 mm N = 45

18 Run time on Dual Xeon with 3 GHz clock rate Fine TLM meshAir vent model 2.5 hours4 min

19 Enclosure with vents & slots a = 50 mm b = 20 mm c = 40 mm = 94.92 mm w = 0.69 mm t = 0.20 mm r = 5.08 mm p = 0.69 mm t = 0.20 mm N = 45

20 Air vents and slots Run time on Dual Xeon with 3 GHz clock fine TLM meshcompact models 2.5 hours3 min 3m from air vent3m from slot

21 Multi-Wire Smart Part Compact vent model sMulti-conductor TL models of wires are connected into the TLM grid sFull coupling between wires and fields sSupports splits, bends, multi-way connections, circuit terminations and ports connector pins cable

22 Near Field Scan Smart Part Emissions sPre-determined near-field scans over entire boards or regions/components can be imported and applied as distributed frequency-dependent (time-varying) sources sIdeal for PCB with 1 or 2 layers where radiation from exposed nets may be important

23 TLM References s 1. Johns P. B. & Beurle R. L., Numerical Solution of 2- Dimensional Scattering Problems Using a Transmission-Line Matrix, Proc. IEE, Vol. 118, No. 9, Sept 1971. s 2. Akhtarzad, S. and Johns, P. B., The solution of Maxwells equations in three space dimensions and time by the TLM method of numerical analysis, Proceedings IEE 122, 12, p.1344-1348, December 1975. s 3. Johns P. B., A symmetrical condensed node for the TLM method, IEEE Trans. Microwave Theory and Techniques, Vol. MTT-35, No. 4, pp. 370-377, 1987. s4. Christopoulos C., The Transmission-Line Modeling Method: TLM, IEEE Press and Oxford University Press, 1995. A volume in the IEEE/OUP Series on Electromagnetic Wave Theory ISBN 0- 7803-1017-9

24 If you have any questions or comments, we welcome your feedback ! Please visit the FLO/EMC web site at and email us at Flomerics Inc. 257 Turnpike Road, Suite 100 Southborough MA 01772 Tel: (508) 357 2012 Flomerics Inc. 1106 Clayton Lane, Suite 525W Austin, TX 78723 Tel: (512) 420 9273 Flomerics Inc. 410 South Melrose Drive, Suite 102, Vista, CA 92083 Tel: (760) 643 4028 Flomerics Inc. 4699 Old Ironsides Drive - #390 Santa Clara, CA 95054-1860 Tel:(408) 562-9100

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