Definition

Crosstalk is electromagnetic coupling between adjacent traces, where a signal on one trace (aggressor) induces noise on a neighboring trace (victim). Forward crosstalk travels in the same direction as the signal; backward crosstalk travels in the opposite direction. Crosstalk increases with trace length, coupling distance, and signal speed. Mitigation includes wider spacing (3x line width rule of thumb), ground shields between traces, stripline routing (better shielding than microstrip), and shorter parallel runs. Crosstalk causes timing jitter and reduces noise margin.