Exam question about TDR measurements

EMC Question of the Week: July 1, 2019

A time-domain reflectometer (TDR) is used to measure a transmission line’s impedance as a function of

  1. time
  2. frequency
  3. temperature
  4. location

Answer

The correct answer is "d". A TDR sends a voltage step signal down a transmission line and monitors the signal reflections. The measured sum of the incident and reflected voltages as a function of time translate to the transmission line’s impedance as a function of location.

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