A Novel Thin Film Bulk Acoustic Resonator (FBAR) Duplexer for Wireless Applications

C. H. Tai; T. K. Shing; Y. D. Lee; C.C. Tien

doi:10.6180/jase.2004.7.2.02

A Novel Thin Film Bulk Acoustic Resonator (FBAR) Duplexer for Wireless Applications

C. H. Tai ¹, T. K. Shing This email address is being protected from spambots. You need JavaScript enabled to view it.¹, Y. D. Lee ² and C. C. Tien²

¹Material Research Laboratory Industrial Technology Research Institute Jhudong, Taiwan 310, R.O.C.
²Department of Electrical Engineering Chung Hua University Hsinchu, Taiwan 300, R.O.C.

Received: December 29, 2003
Accepted: January 16, 2004
Publication Date: June 1, 2004

Download Citation: ||https://doi.org/10.6180/jase.2004.7.2.02

ABSTRACT

A duplexer comprising transmitter (Tx) filter and receiver (Rx) filter using thin film bulk acoustic resonators (FBARs) for use in 1900 MHz PCS band is presented. The typical minimum rejection specifications for Rx filter are > 50 dB in the band of 1850-1910 MHz and for Tx filter are > 40 dB in the band of 1930-1990 MHz. The duplexer requires filters to pose very steep roll-off characteristic because of the very narrow guard band. In the meanwhile, the input impedance must have high impedance in the stopband of each filter to guarantee the receiving signal will go to the Rx filter and the transmitting signal will go to the antenna only. This paper proposes a systematic methodology to design a duplexer to meet all the above requirements using FBARs with minimum auxiliary devices.

Keywords: FBAR, Duplexer, Filter

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