Concepts of signal integrity: crosstalk

Crosstalk crops up in every design. It is one of the most common signal integrity issues that engineers have to deal with. This paper, the third in our series on the concepts of signal integrity, explores the essential principles of crosstalk and what you can do to reduce it.

Two phenomena's of coupling

This paper explains that coupling can happen through two phenomena: capacitive and inductive noise. Because of that, only the switching edge of a signal will contribute
to coupling whereas the steady state section will not. Once a signal couples onto a victim net, the noise will propagate in both directions. The signature of a near-end crosstalk is a wide pulse, whereas the electrical signature of a far-end crosstalk is a narrow pulse. Also shown in this paper is that the biggest noise contributors are the closest aggressors to a victim net.

Essential principles of crosstalk and what you can do to reduce it

Crosstalk is a signal integrity issue that occurs when the signal from one trace couples with another trace, causing interference. There are three essential principles of crosstalk: capacitive coupling, inductive coupling, and conductive coupling.

The first two are the most common and occur when the signal from one trace couples with the signal from another trace through either a capacitor or an inductor. Conductive coupling, on the other hand, occurs when the signal from one trace couples with the signal return path of another trace.

Crosstalk can be controlled by using proper signal routing techniques, impedance control, and shielding. By understanding these principles and utilizing these mitigation techniques, you can help to ensure signal integrity in your designs.

Learn more about Signal Integrity.