Open AccessBalanced RF Duplexer with Low Interference Using Hybrid BAW Resonators for LTE Application
Author(s) -
Shin JeaShik,
Song Insang,
Kim ChulSoo,
Lee MoonChul,
Son Sang Uk,
Kim DuckHwan,
Park HoSoo,
Hwang Sungwoo,
Rieh JaeSung
Publication year - 2014
Publication title -
etri journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.295
H-Index - 46
eISSN - 2233-7326
pISSN - 1225-6463
DOI - 10.4218/etrij.14.0213.0219
Subject(s) - duplexer , resonator , insertion loss , attenuation , materials science , optoelectronics , electronic engineering , interference (communication) , band pass filter , topology (electrical circuits) , electrical engineering , physics , engineering , antenna (radio) , optics , channel (broadcasting)
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‐to‐unbalance 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.