HP ProLiant BL660c Electrical signal integrity considerations for HP BladeSyst - Page 8

Crosstalk

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Crosstalk As current moves through a conductor it creates an electromagnetic field. When two (or more) conductors run parallel to each other, the inductive and capacitive coupling between the paths can lead to interference. This interference is also known as crosstalk. Essentially, crosstalk is the coupling of a signal from one conductor into another adjacent conductor and is exacerbated by increasing transmitted signal speed and reducing the distance between adjacent conductors. Crosstalk results in adding a portion of a signal to its adjacent signals. The externally generated portion of any signal is noise to the original signal. Noise reduces the eye opening and the probability of correctly transferring data on that conductor. Figure 7 depicts the magnetic field that couples two traces and the fact that this coupling diminishes with distance. To the extent possible, the conductors in the board are routed with appropriate spacing to minimize crosstalk. Crosstalk also occurs between the vias in the pin fields of the connectors and in the connectors themselves. These are complex three dimensional structures with non-uniform electric and magnetic fields. Figure 7. Cross sectional view of parallel signal traces depicting electromagnetic fields and their interactions 8

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Crosstalk
As current moves through a conductor it creates an electromagnetic field. When two (or more)
conductors run parallel to each other, the inductive and capacitive coupling between the paths can
lead to interference. This interference is also known as crosstalk. Essentially, crosstalk is the coupling
of a signal from one conductor into another adjacent conductor and is exacerbated by increasing
transmitted signal speed and reducing the distance between adjacent conductors.
Crosstalk results in adding a portion of a signal to its adjacent signals. The externally generated
portion of any signal is noise to the original signal. Noise reduces the eye opening and the
probability of correctly transferring data on that conductor. Figure 7 depicts the magnetic field that
couples two traces and the fact that this coupling diminishes with distance. To the extent possible, the
conductors in the board are routed with appropriate spacing to minimize crosstalk.
Crosstalk also occurs between the vias in the pin fields of the connectors and in the connectors
themselves. These are complex three dimensional structures with non-uniform electric and magnetic
fields.
Figure 7.
Cross sectional view of parallel signal traces depicting electromagnetic fields and their interactions
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