Technical Summary
The Nx2 architecture treats each transmission channel pair as part of two independent channels with no mutual dependency. Unlike the conventional referencing used in differential transmission, Nx2 determines the information carried on each channel relative to the other channel as a reference. This design effectively eliminates the impact of common reference between the two ends of the transmission path.
Additionally, in the Nx2 architecture over twisted pair scenario, each pair represents an independent channel with very close proximity with the other channel, and each of the two independent pairs carries either a positive signal or no signal. This characteristic ensures that any noise affects both pairs equally. The noise influence is then canceled out at the receiver. Furthermore, within the Nx2 receiver, the effect of common mode gain is cancelled out at the comparing stage.
Differential Signaling | Nx2 | |
|---|---|---|
Function of | Ad[V(+)-V(-)]
+Ac[V(+)+V(-)]/2 | Ad1[V1(+)-V1(-)]
-Ad2[V2(+)-V2(-)] |
Common Mode Reference | Fixed | Relative |
Remarks | Performance depends on receiver common mode rejection performance | Common mode is not applicable in this case |
When a 4-pair 0.511 mm (24-AWG) low skew twisted pair cable is employed, each pair is utilized for Nx2 communication as well as for sourcing up-to 90V at 250mA. This configuration enables the delivery of at least 48V at 250mA per pair, even at many hundreds of meters away. Consequently, each pair can provide near 10W at the end of the line, resulting in a total power output of nearly 40W across all four pairs. Of this, 20W powers the destination Nx2 board, while the remaining 20W powers the required end device located away from the source.