EMC Question of the Week: March 11, 2019

Potential Crosstalk Between a Microcontroller Clock and Power Input

To an EMC engineer, NEXT is an acronym for

  1. Near-End Crosstalk
  2. Nominal Extraneous Transmissions 
  3. National Exchange Treaty
  4. Nuclear Excitation Test

Answer

The correct answer is "a." Crosstalk is a measure of the electromagnetic coupling from a source circuit or transmission line to a victim circuit or transmission line. Near-end crosstalk refers to coupling to the end of a victim transmission line nearest the source-end of the source transmission line. Far-end crosstalk (FEXT) refers to coupling to the opposite end of the victim line.  

It's important to note that term "crosstalk" refers to a measure of coupling that can be defined in many different ways. Often, it is defined as a ratio of a voltage measured in the victim circuit to a voltage measured in the source circuit. However, it may also be defined as a power or current ratio. When communicating a value for the crosstalk between two circuits or transmission lines, it is important to convey the definition of crosstalk being employed.

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