Module 4.1 - Crosstalk or near-field coupling - Capacitive coupling, inductive coupling, common-impedance coupling

Crosstalk or near-field coupling - Capacitive coupling, inductive coupling, common-impedance coupling.

Crosstalk is an undesirable effect whereby signals from a loop can create disturbances in another loop. Crosstalk is affected by many factors and this project aims to investigate the effect of circuit impedance on signal crosstalk. Using a setup of three pairs of wires fixed at differing distances apart, signals were transmitted in the aggressor line while the loops are terminated at large impedance (R=∞) moderate impedance (R=50Ω) and low impedance (R=4.7Ω). The frequency and waveform of the signal was varied. A digital oscilloscope was used to observe the behaviour of the near-end and far-end crosstalk in the frequency and time domain. The results show that regardless of circuit impedance, crosstalk increases with higher frequency and decreases with higher separation distance between the loops. At low and high impedance, far and near end crosstalk are similar however at moderate impedance near end crosstalk is slightly higher than far end crosstalk. The time-domain results indicate that at low impedance near and far end crosstalk are anti-phase. At high impedance, far-end and near-end crosstalk are in-phase. Thus, we can better utilize this knowledge to reduce crosstalk in printed circuit boards and cabling, enhancing various electrical systems.