Virtex-5 RocketIO GTP Transceiver User Guide
241
UG196 (v1.3) May 25, 2007
SMT Pads
R
Next, using simulated measurements on the same transition modeled in HFSS, the time-
domain performance of this transition can be measured by doing a TDR on the
S-parameter results from the earlier frequency domain analysis.
, the red curve with the large capacitive dip corresponds to
the SMT pad without the ground plane cleared from underneath. The blue curve shows
that clearing out the ground plane removes much of the excess capacitance. This
improvement can be quantified using
and
.
Figure 13-7:
Return Loss Comparison Between 0402 Pad Structures
Figure 13-8:
Return Loss Comparison Between 0402 Pad Structures on Log
(Frequency) Scale
0
-20
-40
-60
0
2
4
6
Frequency, GHz
8
Cleared Planes
Uncleared Planes
10
dB(S(3,3))
dB(S(1,1))
UG196_c13_07_051406
0
-20
-40
-60
1E8
1E9
Frequency, Hz
+40dB/Decade RL Slope Shows a
Good Fit to Lumped Capacitance
1E10
dB(S(3,3))
dB(S(1,1))
UG196_c13_08_051406
Содержание Virtex-5 RocketIO GTP
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Страница 88: ...88 www xilinx com Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007 Chapter 5 Tile Features R...
Страница 122: ...122 www xilinx com Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007 Chapter 6 GTP Transmitter TX R...
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Страница 222: ...222 www xilinx com Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007 Section 2 Board Level Design R...
Страница 256: ...256 www xilinx com Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007 Section 3 Appendices R...
Страница 312: ...312 www xilinx com Virtex 5 RocketIO GTP Transceiver User Guide UG196 v1 3 May 25 2007 Appendix E Low Latency Design R...