EMC Question of the Week: September 18, 2023

A twisted wire pair, a shielded wire pair, a coaxial cable and a rectangular waveguide

A 1-Gbps signal propagates from a single-ended source on a microstrip trace to a connector. Which cable option would be appropriate to convey this signal to another circuit board 1 meter away?

  1. twisted wire pair
  2. shielded wire pair
  3. coaxial cable
  4. rectangular waveguide


The best answer is “c.” Since the source is unbalanced, it should employ an unbalanced transmission line. Wire pairs, whether twisted or shielded, are balanced transmission lines. The rectangular waveguide is unbalanced, but impractical. Of the choices provided, the coaxial cable is the only viable option. 

For shorter distances, another unbalanced transmission line to consider would be a flexible circuit board with a solid return plane. If the distance were 10 cm or less, this might be a lower-cost option than a coaxial cable.

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