Dual-Stacked Connector
sims-2-TDR/EMI correlation of
Impedance & Emission-Radiation
Hany M Fahmy
May 13th , 2008
1

Model of the connector
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.
2

E-field plots using Waveguide ports
to compute the input-impedance @
the ports
3

Odd-mode @ brd-side: Pin-set-1
E-field plots @ brd-side showing line-impedance of ~ 180-ohms
4

Odd-Mode @ brd-side: Pin-set-2
E-field plots @ brd-side showing line-impedance of ~ 199-ohms
5

Odd-Mode @ brd-side: Pin-set-3
E-field plots @ brd-side showing line-impedance of ~ 203-ohms
6

IL and RL using Discrete Ports
1
3
5
Cable-side
2
4
6
Brd-side
7

Discrete Ports
8

Return Loss: S11, S22, S33,S44,
S55 & S66
Dip from 800MHz to 850MHz: good for Return-Loss
9

Insertion-loss: S12,S21,S34,
S43,S56,S65
Dip from 800MHz to 850MHz: Bad for Insertion-loss S12, S34, S56: brd-side
10

What happened to the Insertion-PWR
800MHz to 850MHz?
Dip from 812MHz to 860MHz: Radiation Power on brd-side: Reaching as high
as 20% of power radiated
11

Radiated emission peaks
@ 778MHz and 814MHz
12

NEXT & FEXT
NEXT and FEXT are better than -18dB except in the range of 800MHz to
850MHz up to -8.5dB
13

Surface Current on EMI-shield @ 1GHz
Amplitude of surface current showing hot-spots on the EMI-shield
EMI-shield provide surface-2-surface coupling better reference than the
edge-2-edge coupling provided by the GND-pins
14

Surface Current on interior
@ 1GHz
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
15

Surface Current Movie:
use slide-show mode
16

Correlation with TDR measurement of
the TOP-DVI connector
TOP (no board)
TOP on P348A02
TOP on P607 board
TDR the connector without soldering-down does show a small-knee as in the red-signal,
17
Once the connector is soldered-down, then we see large peak of impedance ~ 180-ohms

Summary
• Sims correlate to TDR meas showing that the deffimpedance @ 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
18