Crosstalk (electronics)

For other uses, see Crosstalk (disambiguation).

Not to be confused with Spill (audio).

In electronics, crosstalk (XT) is any phenomenon by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Crosstalk is usually caused by undesired capacitive, inductive, or conductive coupling from one circuit, part of a circuit, or channel, to another.

Crosstalk in cabling

In structured cabling, crosstalk can refer to electromagnetic interference from one unshielded twisted pair to another twisted pair, normally running in parallel.

Near End Crosstalk (NEXT)

Interference between two pairs in a cable measured at the same end of the cable as the transmitter.

Far end crosstalk (FEXT)

Interference between two pairs of a cable measured at the other end of the cable from the transmitter.

Alien crosstalk (AXT)

Interference caused by other cables routed close to the cable of interest.^[1]

Other examples

In telecommunication or telephony, crosstalk is often distinguishable as pieces of speech or signaling tones leaking from other people's connections.^[2] If the connection is analog, twisted pair cabling can often be used to reduce the effects of crosstalk. Alternatively, the signals can be converted to digital form, which is much less susceptible to crosstalk.

In wireless communication, crosstalk is often denoted co-channel interference, and is related to adjacent-channel interference.^{[clarification needed]}

In integrated circuit design, crosstalk normally refers to a signal affecting another nearby signal. Usually the coupling is capacitive, and to the nearest neighbor, but other forms of coupling and effects on signal further away are sometimes important, especially in analog designs. See signal integrity for tools used to measure and prevent this problem, and substrate coupling for a discussion of crosstalk conveyed through the integrated circuit substrate. There are a wide variety of possible fixes, with increased spacing, wire re-ordering, and shielding being the most common.

In a music recording setting, the term "crosstalk" can refer to the leakage or "bleeding" of sound from one instrument into a microphone placed in front of another musical instrument or singer. A common example is the leakage of the high-pitched, heavily-amplified sound of the lead guitar into the microphones for other instruments. Note that this is nearly always an acoustic effect, not electrical.

In stereo audio reproduction crosstalk can refer to signal leaking across from one program channel to another. This is an electrical effect and can be quantified with a crosstalk measurement.

In full-field optical coherence tomography, "crosstalk" refers to the phenomenon that due to highly scattering objects, multiple scattered photons reach the image plane and generate coherent signal after traveling a pathlength that matchs that of the sample depth within a coherence length.

In Stereoscopic 3D Displays, "crosstalk" refers to the incomplete isolation of the left and right image channels so that one leaks or bleeds into the other - like a double exposure. In this area, crosstalk and ghosting are often used interchangeably, however crosstalk is a physical entity and can be objectively measured, whereas ghosting is a subjective term and refers to the perception of crosstalk.

See also

• Audio system measurements
• Co-channel interference (CCI)
• Signal integrity
• Substrate coupling
• Signal-to-interference ratio (SIR or S/I), also known as carrier-to-interference ratio (CIR or C/I)
• Unger model
• Attenuation-to-crosstalk ratio
• MIL-STD-188
• Federal Standard 1037C

References

1. ^ Eliminating alien crosstalk, Communications News, February 2009, http://www.comnews.com/features/2009_february/0209_web3_eliminating.aspx, retrieved 2010-08-19 
2. ^ Federal Standard 1037C glossary Archived 2011-10-24.

External links

• Educational slideshow on capacitive and inductive crosstalk
• Minimizing Crosstalk in Wiring and Cabling