What is Crosstalk?
Editorial Team - EMC Directory
What is Crosstalk?
Crosstalk is a phenomenon in which signals in one wire/cable/circuit induce electromagnetic interference(EMI) in an adjacent wire/cable/circuit. This happens because the signals traveling through the transmission medium are susceptible to attenuation, distortion, and noise. It is particularly prevalent in communication systems that employ copper wires, such as UTP or coaxial cables.
The primary cause of crosstalk lies in the coupling between signals transmitted via parallel adjacent cables. This coupling can occur through electrostatic or electromagnetic induction. Each analog signal generates an associated magnetic or electric field, and when these fields overlap with those of neighboring signals, they create disturbances and induce interference in other signals. This interference manifests as crosstalk, corrupting the original signal during transmission.
In the context of twisted-pair cabling, these are the types of crosstalk that are commonly encountered:
Near-End Crosstalk (NEXT): Near-End Crosstalk occurs at the near end of the cable from where the signal is transmitted. It is a significant concern in twisted pair cables, such as Ethernet cables.
Far-End Crosstalk (FEXT): Far-End Crosstalk occurs at the far end of the cable from where the signal is transmitted. It becomes a concern when multiple parallel cables are nearby, such as in bundle or trunk cables.
Equal Level Far-End Crosstalk: ELFEXT is measured at the far end of the cable where the receiving pair is located. It indicates the signal degradation caused by interference from neighboring pairs on the same cable.
Power Sum Near-End Crosstalk (PSNEXT): PSNEXT, also known as Pair-to-Pair NEXT or SumNEXT, is a measurement of crosstalk that considers the cumulative effect of crosstalk from multiple neighboring pairs onto a specific pair. It takes into account the combined interference caused by all adjacent pairs on the same cable.
Power Sum Far-End Crosstalk (PSFEXT): PS-ELFEXT takes into account the cumulative effect of crosstalk from multiple adjacent pairs on the same cable, similar to Power Sum
Near-End Crosstalk (PSNEXT). However, PS-FEXT specifically measures the interference at the far end of the cable, where the receiving pair is located.
Power Sum Equal-Level Far-End Crosstalk (PS-ELFEXT): refers to the combined crosstalk effect from adjacent pairs on the far end of a twisted pair cable onto the pair on the near end. PS-ELFEXT can be calculated by adding the values of Power Sum Near-End Crosstalk (PSNEXT) and Power Sum Far-End Crosstalk (PSFEXT).
Alien Crosstalk (AXT): Alien Crosstalk occurs between different cables, typically in bundled or parallel configurations. It refers to the interference caused by one cable onto another adjacent cable. AXT is a significant concern in high-density cabling environments where multiple cables are located closely together.
In stereo audio reproduction, crosstalk refers to the phenomenon of signal leakage between program channels, leading to a reduction in channel separation and stereo imaging. This issue becomes more pronounced in mixing consoles and studio feeds where different programs or materials are being carried.
The two main types of crosstalks which can occur are:
Interchannel Crosstalk: Interchannel crosstalk refers to the leakage of audio signals between the left and right channels in a stereo system. It occurs when the signals intended for one channel bleed into the other channel, leading to a reduction in channel separation. This can result in a loss of clarity and stereo imaging, affecting the overall audio experience.
Intersignal Crosstalk: Intersignal crosstalk, also known as program crosstalk, occurs when signals from different audio sources or programs interfere with each other. This type of crosstalk can arise in mixing consoles or studio feeds where multiple audio signals are present.
Intersignal crosstalk can cause undesired mixing of audio content, resulting in an inaccurate representation of the original signals.