Crosstalk Analysis For Xmultiple Connectors

   
 

From Xmultiple Engineering Dept.


 

Crosstalk (XT)

Crosstalk (XT) in the electronics industry refers to any condition by which a signal transmitted on one circuit or channel of a transmission system creates an undesired effect in another circuit or channel. Therefore crosstalk is also referred to as the effect seen on a circuit from neighboring signals. 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.

There are two types of crosstalk in a transmission:

1. Far-end crosstalk (FEXT) which is the noise a channel hears from a neighboring channel. FEXT is the noise on the opposite side of the circuit or when reference this noise in relationship to a connector it would be at the other end of the connector.

2. The second type of crosstalk is Near-end crosstalk (NEXT). NEXT is the effect a channel might experience from a nearby channel on the same end of the circuit. In relationship to connectors this would be on the same side of the connector.

Many customer ask how we test for each of these types of crosstalk?

First, We Inject a signal into a neighboring differential pair (aggressor) and
listen to the effect it has on our focus differential pair (victim). Our engineers then run this test with each of the neighboring circuits and provide the data. The data is to see how our focus signal may be affected. In Summary, the test is to see the effects the neighboring circuits have on a certain circuit in the connector which is being tested.

As a rule of thumb, the crosstalk value is around 5%, If the value is larger for the crosstalk this means the crosstalk is having a significant effect on signal performance. Therefore engineers and designers target crosstalk in the 5% range or lower.

The shielding of connectors and the plating has significant influences on crosstalk and therefore these are the tested carefully by our engineers. The plastic housing material and design are analyzed as well so Crosstalk has a minimal effect in regards to our connectors.

CAT5, CAT5e, CAT6 and CAT7 Information


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