Two Tunable Frequency Duplexer Architectures for Cellular Transceivers

Research output: Contribution to journalArticle


In this paper two architectures for tunable duplexers
are presented. The tuning is accomplished through variable
capacitance and resistance. The architectures are based on a
three element series-parallel resonator, with one pass and one
stop frequency. Both architectures rely on filtering as well as
cancellation for good Tx to Rx isolation while maintaining low
insertion loss. The first architecture, the Filtered Transformer
Balanced (FTB) isolator, has single ended transmit and antenna
ports and a differential receive port. The second architecture,
the Cross Coupled Filtering (CCF) isolator, is fully differential.
For a resonator Q of 50, the impedance ratio of the resonator at
pass and stop frequencies is 18.5dB for 3GPP band-I. In the FTB
isolator this results in 1.65dB Tx and 2.14dB Rx insertion loss,
and 53 dB isolation for a 20 MHz channel bandwidth. In the CCF
isolator this results in 1.9dB Tx and 1.9dB Rx insertion loss, and
59dB isolation for a 20 MHz channel bandwidth. These figures
are obtained with a 20% resistive mismatch, showing feasibility of
good performance in an environment with changing impedance.
As the operating frequencies of cellular systems increase, these
structures will become fully integratable due to the reduced sizes
of inductors and transformers.


External organisations
  • Ericsson AB
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Other Electrical Engineering, Electronic Engineering, Information Engineering
Original languageEnglish
Number of pages12
JournalIEEE Transactions on Circuits and Systems I: Regular Papers
Publication statusPublished - 2017 Jun 7
Publication categoryResearch