Optimum single antenna full duplex using hybrid junctions

Leo Laughlin*, Mark A. Beach, Kevin A. Morris, John L. Haine

*Corresponding author for this work

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

58 Citations (Scopus)
362 Downloads (Pure)


This paper investigates electrical balance (EB) in hybrid junctions as a method of achieving transmitter-receiver isolation in single antenna full duplex wireless systems. A novel technique for maximizing isolation in EB duplexers is presented, and we show that the maximum achievable isolation is proportional to the variance of the antenna reflection coefficient with respect to frequency. Consequently, antenna characteristics can have a significant detrimental impact on the isolation bandwidth. Simulations that include embedded antenna measurements show a mean isolation of 62 dB over a 20-MHz bandwidth at 1.9 GHz but relatively poor performance at wider bandwidths. Furthermore, the operational environment can have a significant impact on isolation performance. We present a novel method of characterizing radio reflections being returned to a single antenna. Results show as little as 39 dB of attenuation in the radio echo for a highly reflective indoor environment at 1.9 GHz and that the mean isolation of an EB duplexer is reduced by 7 dB in this environment. A full duplex architecture exploiting EB is proposed.

Original languageEnglish
Article number6832460
Pages (from-to)1653-1661
Number of pages9
JournalIEEE Journal of Selected Areas in Communications
Issue number9
Publication statusPublished - Sep 2014

Bibliographical note

E-pub ahead of print 12 Jun 2014


  • Duplexers
  • full-duplex
  • hybrid junctions
  • interference cancellation
  • self-interference


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