LANcat
User Manual
Page 7-16
POWER SUM NEXT
Power Sum NEXT is a critical test for certifying the performance
of installed twisted pair links. It is the sum of the pair-to-pair
NEXT coupled from all adjacent pairs in a cable.
Power Sum NEXT is an important measurement for emerging high
speed local area networks such as 622 Mbps ATM and Gigabit
Ethernet. These networks transmit over multiple pairs at once to
achieve their high data rates. Because they transmit over several
pairs simultaneously, the normal pair-to-pair NEXT is not
indicative of the coupled noise signal into the receive pair. Rather,
the coupled signal is larger due to the multiple transmitters.
Crosstalk from multiple pairs is illustrated below in Figure 7-9.
Signal generators
Signal measurement
1
2
3
6
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5
M
7
8
Crosstalk
Figure 7-9. Power Sum NEXT Measurement
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