Balanced RF duplexer with low interference using hybrid BAW resonators for LTE application

Jea Shik Shin, Insang Song, Chul Soo Kim, Moon Chul Lee, Sang Uk Son, Duck Hwan Kim, Ho Soo Park, Sungwoo Hwang, Jae Sung Rieh

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)


A balanced RF duplexer with low interference in an extremely narrow bandgap is proposed. The Long-Term Evolution band-7 duplexer should be designed to prevent the co-existence problem with the WiFi band, whose fractional bandgap corresponds to only 0.7%. By implementing a hybrid bulk acoustic wave (BAW) structure, the temperature coefficient of frequency (TCF) value of the duplexer is successfully reduced and the suppressed interference for the narrow bandgap is performed. To achieve an RF duplexer with balanced Rx output topology, we also propose a novel balanced BAW Rx topology and RF circuit block. The novel balanced Rx filter is designed with both lattice- and ladder-type configurations to ensure excellent attenuation. The RF circuit block, which is located between the antenna and the Rx filter, is developed to simultaneously function as a balance-tounbalance transformer and a phase shift network. The size of the fabricated duplexer is as small as 2.0 mm × 1.6 mm. The maximum insertion loss of the duplexer is as low as 2.4 dB in the Tx band, and the minimum attenuation in the WiFi band is as high as 36.8 dB. The TCF value is considerably lowered to -16.9 ppm/°C.

Original languageEnglish
Pages (from-to)317-320
Number of pages4
JournalETRI Journal
Issue number2
Publication statusPublished - 2014 Apr


  • BAW
  • Bulk acoustic wave
  • FBAR
  • Film bulk acoustic wave resonator
  • RF duplexer
  • RF resonator

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • General Computer Science
  • Electrical and Electronic Engineering


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