#### sp2821

##### Newbie level 4

If I understand correctly, characteristic impedance of a transmission line is ratio of forward voltage wave to forward current wave or reflected voltage wave to reflected current wave.

It makes sense that Z_0 = (V+/I+). But why is Z_0=-(V-/I-)?

I searched for answers online and only explanation I found was "minus sign is because I- is traveling in -Z direction"

But V- is also traveling in same direction (-Z direction). So shouldn't minus signs cancel out and Z_0=(V-/I-)?

Thanks,