Signal Balancing in Unbalanced Transmission Lines

Jonathan Munoz-Enano, Paris Velez, Ferran Martin

Research output: Contribution to journalArticleResearch

5 Citations (Scopus)


© 1963-2012 IEEE. Balanced lines operating as transmission line interconnects are subjected to differential-mode to common-mode conversion (and vice versa) in situations where symmetry imbalances (e.g., caused by line bends) are unavoidable. In this paper, a technique to compensate for such symmetry imbalances, providing pure differential-mode signals at the differential output port of the line, is presented. Such technique uses a rat-race balun (to generate the differential-mode signal) with the isolated port conveniently loaded, and it is based on the modification of the characteristic impedance of one of the unbalanced lines. A detailed analysis that justifies this compensation technique (valid for any arbitrary four-port network) and provides the design equations is presented. The approach is validated through simulation and experiment, by demonstrating that common-mode signals are not transmitted to the differential output port of a bended (i.e., unbalanced) line pair.
Original languageEnglish
Article number8753521
Pages (from-to)3339-3349
JournalIEEE Transactions on Microwave Theory and Techniques
Publication statusPublished - 1 Aug 2019


  • Balanced lines
  • common mode
  • differential mode
  • microstrip
  • rat-race coupler


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