Hybrid Bulk Acoustic Wave Structure for Temperature Stability in LTE Applications

• Published in: IEEE microwave and wireless components letters 2013-09, Vol.23 (9), p.453-455
• Main Authors: SHIN, Jea-Shik, INSANG SONG, RIEH, Jae-Sung, KIM, Chul-Soo, SANG UK SON, LEE, Moon-Chul, KIM, Duck-Hwan, PARK, Ho-Soo, JING CUI, YUJIE AI, SUNGWOO HWANG
• Format: Article
• Language: English
• Subjects: Acoustic waves; Applied sciences; Bulk acoustic wave (BAW) resonator; Circuit properties; Electric, optical and optoelectronic circuits; Electronic circuits; Electronics; Exact sciences and technology; Frequency filters; IEEE 802.11 Standards; Impedance; Q-factor; Resonant frequency; RF duplexer; RF filter; Switching, multiplexing, switched capacity circuits; temperature coefficient of frequency (TCF); Temperature measurement
• ISSN: 1531-1309; 1558-1764
• DOI: 10.1109/LMWC.2013.2272609

A novel structure of hybrid bulk acoustic wave (BAW) resonator with low temperature coefficient of frequency (TCF) is presented. Implemented with a pair of quarter-wave reflectors on air-cavity reflector, the hybrid BAW resonator exhibits a TCF of as low as -11.5 ppm/°C and an effective electro-mechanical coupling coefficient (kt 2 ) of 5.1% at the frequency of 2.5 GHz. The hybrid BAW resonator also shows excellent Q-factors of 1627 and 1842 at resonance and anti-resonance frequency, respectively. RF duplexer configured with the hybrid BAW resonators is provided as well. The fabricated RF duplexer for long term evolution (LTE) band-7, which should be designed to prevent the co-existence problem with WiFi having extremely narrow fractional band-gap of 0.7%, achieves an attenuation of 36.8 dB and an insertion loss of 2.4 dB.