Does VSWR affect Crosstalk? 3

[bpelec]

As I understand it, VSWR is a measure of how much of a signal gets reflected back to the source in a transmission line, and crosstalk is a measure of how much coupling exists between channels in a transmission line system.

Is there a relationship between VSWR and crosstalk?

For example, I have identified two points of impednace mis-match in a 'transmission line' using TDR (time domain reflectometry). I assume that these two points of mismatch will make the VSWR worse. Does it also follow that the crosstalk will be worse due to these two points?

Thank you for your help!

Best regards,

BPELEC.

 

[logbook]

There is no general relationship between cross-talk and VSWR.

As you have pointed out, VSWR is a measure of mismatch at an input. (VSWR can be calculated from the reflection coefficient).

Cross-talk is a measure of coupling between two apparently unconnected but nearby systems. The two effects may be coupled on any particular system, but there is no general connection. Mis-match need not be due to adjacent channel coupling.

 

[zappedagain]

Logbook is correct, and to state it the other way, there is no general relationship between VSWR and crosstalk.

An impedance mismatch will give a reflection that will put higher voltages at some points along the transmission line and higher currents at other points along the t-line. Crosstalk is due to coupling - capacitive coupling of the voltage, or inductive coupling of the current. If your reflection happens to cause a V or I increase at a point where the coupling is high you will get more crosstalk. So while you are correct that high VSWR can effect your crosstalk, it isn't a linear effect; it might get much worse or there may be negligible change.

Your crosstalk could be a partial cause of the VSWR too; if you have a lot of coupling to adajacent lines your characteristic impedance may not be what you designed for.

 

[Comcokid]

There is not general relationship between the two. However, in a coaxial system feeding into a non-coaxial, a mismatch may cause the reflected energy to flow back down the outside of the coax. This reflection down the shield of the coax may then be coupled into adjacent wires or cables. Such situations usually happen at the feed point of antennas, and a choke on the outside of the coax may be used to reduce effect.