Tunable Frequency-Division Duplex RF Front End Using Electrical Balance and Active Cancellation

Leo Laughlin, Chunqing Zhang, Mark A. Beach, Kevin A. Morris, John L. Haine, Muhammad Kalimuddin Khan, Michael McCullagh

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

22 Citations (Scopus)
620 Downloads (Pure)


This paper presents a novel, tunable, frequency-division duplexing radio frequency (RF) front end that combines passive and active self-interference (SI) cancellation. An electrical-balance duplexer is used to passively cancel transmitter noise in the receive band, and an active canceller is employed to suppress SI in the transmit (Tx)-band. Subsystem specifications are developed, and a system-level analysis of noise and SI powers in this novel architecture is provided, thereby illustrating its operation. A proof-of-concept demonstrator, built from a software-defined radio and discrete RF components, has been characterized across a range of duplex configurations in the 700-950-MHz range and also at 1900 (Long-Term Evolution (LTE) band 3) and 2600 MHz (LTE band 7). The prototype achieves an impressive 6.0-7.4-dB noise figure in the presence of a +27-dBm LTE uplink Tx blocker for duplex separations of 47.5 MHz and above. The duplexer has also been tested against reference sensitivity test cases defined in the 3GPP LTE specification, demonstrating specification compliant sensitivity in LTE bands 28 (700 MHz), 3, and 7.

Original languageEnglish
Pages (from-to)5812-5824
Number of pages13
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number12
Early online date23 Jul 2018
Publication statusPublished - 1 Dec 2018


  • 5G mobile communication
  • Duplexer
  • electrical balance
  • frequency-division duplex (FDD)
  • in-band full duplex (IBFD)
  • self-interference cancellation (SIC)
  • tunable filters.


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