Electronic – Information regarding DC wander


I was just going through a text book on digital communication where something related to ac coupling was mentioned.It was mentioned that if a long stream of one(1) is encountered at the receiving end then an erroneous bit is supposed to occur (sorry for not being able to quote the text).So for that purpose they are somewhat DC balanced in order to avoid DC WANDER.

I tried to look for it but did not get a proper, thirst quenching response.
Is it possible to get a conceptual explanation for what they mean by DC wander?

Best Answer

Visualisation aid:

  • "All models are wrong.
    Some models are useful" ... George Box.

Imagine feeding a signal through a capacitor.

If you send AC (sine or square waves etc) with a mean DC level of zero, then the signal passes through it unimpeded.

If you apply DC to a capacitor it will charge exponentially to the driving voltage and current flow will fall exponentially to zero - a capacitor does not pass DC..

A comms channel of the sort you are dealing with is effectively an AC coupled circuit. You must maintain the AC nature of the signal so that it does not "appear to be DC".