Specifications

Intel
®
810E2 Chipset Platform
R
124 Design Guide
4.2.3. Crosstalk Theory
AGTL+ signals swing across a smaller voltage range and have a correspondingly smaller noise margin
than technologies that have traditionally been used in personal computer designs. This requires that
designers using AGTL+ be more aware of crosstalk than they may have been in past designs.
Crosstalk is caused through capacitive and inductive coupling between networks. Crosstalk appears as
both backward crosstalk and as forward crosstalk. Backward crosstalk creates an induced signal on a
victim network that propagates in a direction opposite that of the aggressor’s signal. Forward crosstalk
creates a signal that propagates in the same direction as the aggressor’s signal. On the AGTL+ bus, a
driver on the aggressor network is not at the end of the network; therefore it sends signals in both
directions on the aggressor’s network. The figure below shows a driver on the aggressor network and a
receiver on the victim network that are not at the ends of the network. The signal propagating in each
direction causes crosstalk on the victim network.
Figure 71. Aggressor and Victim Networks
Victim
Aggressor
Zo
Signal Propagates in both
directions on agressor line.
Zo
Zo
Zo
aggres_victim.vsd
Figure 72. Transmission Line Geometry: (A) Microstrip (B) Stripline
AC Ground Plane
A. Microstrip
B. Stripline
Dielectric,
ε
r
Signal Lines
Signal Lines
Dielectric,
ε
r
W
Sp
t
trans_line_geom.vsd