i know that a ferrite bead or a resistor is used to couple the analogue ground and digital ground in schematic and in layout .
could anybody pls explain me y we are using a resistor or ferrite bead to couple the same in detail
It is better to use to ferrite bead, because ferrite bead doesn't allow ac ripples and digital ground doesn't have ac ripples.
So ferrite bead is the good option.