Power Over Ethernet Interoperability Guide

Current-Imbalance I_UNB: What Is It Really?

Let us recapitulate what we learned in Fig. 9.3. We defined resistive imbalance in a slightly nonintuitive way. If the resistance in one branch was 6 percent larger than the resistance in the other branch, the resistive imbalance was 3 percent. Since currents entering a parallel network distribute in inverse proportion to resistance, the current in one branch was also 6 percent more than the current in the other branch. However, since the split current halves were roughly half of the total port current, this 6 percent translated into 6%/2 = 3% of the total port current. That was the DC bias. So DC bias was calculated to be 3 percent of the total port current.

Now we make an observation: What exactly ...