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Dual-Stacked Connectorsims-2-TDR/EMI correlation of
Impedance & Emission-Radiation
Hany M Fahmy
May 13th , 2008
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Model of the connector
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Mechanical model was not complete, we got the real connector and added GND-patches to connect the shields, also added a load-brd as if
the connector is soldered-down to the brd.
E-field plots using Waveguide ports to compute the input-impedance @
the ports
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Odd-mode @ brd-side: Pin-set-1
4E-field plots @ brd-side showing line-impedance of ~ 180-ohms
Odd-Mode @ brd-side: Pin-set-2
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E-field plots @ brd-side showing line-impedance of ~ 199-ohms
Odd-Mode @ brd-side: Pin-set-3
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E-field plots @ brd-side showing line-impedance of ~ 203-ohms
IL and RL using Discrete Ports
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1
3
5
2
4
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Cable-side Brd-side
Discrete Ports
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Return Loss: S11, S22, S33,S44, S55 & S66
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Dip from 800MHz to 850MHz: good for Return-Loss
Insertion-loss: S12,S21,S34,S43,S56,S65
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Dip from 800MHz to 850MHz: Bad for Insertion-loss S12, S34, S56: brd-side
What happened to the Insertion-PWR 800MHz to 850MHz?
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Dip from 812MHz to 860MHz: Radiation Power on brd-side: Reaching as high as 20% of power radiated
Radiated emission peaks @ 778MHz and 814MHz
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NEXT & FEXT
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NEXT and FEXT are better than -18dB except in the range of 800MHz to 850MHz up to -8.5dB
Surface Current on EMI-shield @ 1GHz
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Amplitude of surface current showing hot-spots on the EMI-shieldEMI-shield provide surface-2-surface coupling better reference than the
edge-2-edge coupling provided by the GND-pins
Surface Current on interior @ 1GHz
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GND-pins can not handle a lot of the return-current as it is edge-2-edge coupling worse than the EMI-shield which is surface-2-surface coupling
Surface Current Movie: use slide-show mode
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Correlation with TDR measurement of the TOP-DVI connector
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TDR the connector without soldering-down does show a small-knee as in the red-signal, Once the connector is soldered-down, then we see large peak of impedance ~ 180-ohms
TOP on P607 board
TOP (no board)
TOP on P348A02
Summary
• Sims correlate to TDR meas showing that the deff-impedance @ brd-side is ranging from 180-ohms to 200-ohms
• Sims drove the need for soldered-down connector as BKM for TDR measurements on the connector to capture such impedance impact (out-of-spec)
• Power Balance show that radiated emission peaks @ 778MHz and also 814Mhz close-by the actual emission problems
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