Passive and Active Electrical Balance Duplexers

Leo Laughlin, Chunqing Zhang, Mark A Beach, Kevin A Morris, John L Haine

Research output: Contribution to journalArticle (Academic Journal)peer-review

35 Citations (Scopus)
638 Downloads (Pure)


Electrical balance duplexing enables simultaneous transmit and receive from a single antenna, however the transmit-to-receive isolation depends on the ability of the balancing algorithm to determine the correct balancing impedance. A novel balancing algorithm based on in-situ characterization of the duplexer self-interference channel is proposed. The algorithm requires no a-priori knowledge of the antenna impedance or hybrid junction characteristics, and automatically compensates for circuit imperfections. novel balancing network implementation which uses active signal injection is also proposed. A hardware prototype implementing the proposed balancing algorithm and combining passive and active balancing techniques has achieved 81.5dB isolation over an 80MHz bandwidth.
Original languageEnglish
Pages (from-to)94-98
Number of pages5
JournalIEEE Transactions on Circuits and Systems II: Express Briefs
Issue number1
Early online date25 Sept 2015
Publication statusPublished - Jan 2016


  • Duplexers
  • Full-duplex
  • Electrical Balance Duplexer
  • Self-interference cancellation
  • 5G enabling technologies


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