Development of Miniature Surface Acoustic Wave Duplexer for Wide-band Code-Division Multiple-Access System

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1 Development of Miniature Surface Acoustic Wave Duplexer for Wide-band Code-Division Multiple-Access System Hiroyuki Nakamura Hidekazu Nakanishi Tetsuya Tsurunari Ken Matsunami Yukio Iwasaki SiO 2 AlLiNbO 3 W-CDMAWide-band Code Division Multiple Access 2 GHzW-CDMA SiO 2 AlLiNbO 3 2 SiO mm 2.0 mmw-cdmasaw Surface Acoustic Wave A miniature Surface Acoustic Wave Duplexer for Wide-band Code-Division Multiple-Access System (W-CDMA) using SiO 2 /Al/LiNbO 3 structure has been developed. The W-CDMA system at 2 GHz has a wide duplex gap between transmitting and receiving bands. The structure has the advantage of a large electromechanical coupling coefficient for miniaturization. However, it also supports a certain number of unwanted spurious responses. They are categorized into two types: one is caused by the Rayleigh mode and the other by the transverse mode. The former can be suppressed by controlling the cross-sectional shape of the SiO 2 overlay deposited on resonator electrodes. The latter can be suppressed by using the new scattered dummy electrode weighting. We applied the techniques to the development of a miniature W-CDMA duplexer with a package size of 2.5 mm2.0 mm, and the duplexer exhibited excellent performance. SAW W-CDMA SAW SAW SAW SAW 2 GHzW-CDMA 1920 MHz-1980 MHz 2110 MHz-2170 MHz130 MHz 36-48Y-cut LiTaO 3 10 % Y LiNbO 3 1), 2) SiO 2 3) IDTInterdigital TransducerAl 4) Cu 5) SiO 2 AlYLiNbO 3 2 GHzW-CDMASAW SAW 1SAWSAW

2 Alh Al SAW Structure of SAW duplexer SAW 2 SAW SAW 2 GHzW-CDMA 15 % SiO 2 AlLiNbO 3 2K 2 YLiNbO 3 SiO 2 AlLiNbO 3 SAW IDT p1 msio 2 h SiO2 SAW0.2 2Al h Al K 2 15 % 3SAW2 YLiNbO 3 h Al 45SAW h Al =0.03 h Al = W-CDMASAW YLiNbO 3 Electromechanical coupling coefficient dependence of LiNbO 3 cut angle Minimum insertion loss dependence of LiNbO 3 cut angle =5SAW Admittance characteristics of SAW resonator in case of =5 IDTSiO 2

3 4.1 5SiO 2 AlLiNbO 3 IDT SiO 2 5 ABCSiO 2 6) ACSAW Transmission performances of SAW resonators with SiO 2 shapes A, B, and C SiO 2 AlLiNbO 3 Cross-sectional view of SiO 2 /Al/LiNbO 3 structure SiO 2 SAW ph Al h SiO2 1.0 m IDT m SiO 2 A B C ABC SiO IDT SAW 6ACSAW 6SiO 2 C SiO 2 CSAW 110 MHz15 % W-CDMASAW SiO 2 C SiO ) SAW 7SAW SAW Structure and crass-sectional view of SAW resonator

4 IDT SiO 2 IDT SAWp 0.9 m5idt msaw 8 SAW Structure and cross-sectional view of SAW resonator with scattered dummy electrode weighting SAW Transmission performance of SAW resonator SiO 2 AlLiNbO 3 SAW 9 SiO 2 SAW 1010 SAW 0.18 db SiO 2 SAW Transmission performance of SAW resonator with scattered dummy electrode weighting 2 GHzW-CDMASAWSiO 2 Al LiNbO mm 2.0 mmidtsaw AlMgCuTi 8) SAW db45 db 1.9 db51 db db 45 dbsaw -30 ppm/saw 2 GHzW-CDMA

5 Transmitting characteristics of SAW duplexer SAW Receiving characteristics of SAW duplexer SAW Isolation of SAW duplexer SAW SiO 2 AlYLiNbO 3 2 GHzW-CDMASAW SiO 2 15 %2 GHzW- CDMA SAW2.5 mm2.0 mm 3.0 mm2.5 mm 1K. Yamanouchi, et al. : Propagation and amplification of Rayleigh waves and piezoelectric leaky surface waves in LiNbO 3. J. Appl. Phys. 43,pp (1972). 2K. Hashimoto, et al. : Ultra-wideband surface acoustic wave devices using Cu-grating/rotated-YX-LiNbO 3 substrate structure. Jpn. J. Appl. Phys. 43,pp (2004). 3K. Yamanouchi, et al. : High temperature stable high electromechanical coupling substrates and application for surface acoustic wave devices. Proc. IEEE Ultrason. Symp. pp (2001). 4K. Yamanouchi, et al. : Theoretical and experimental results of ultrawide-band zero-tcf ladder-type SAW filters and arbitrary bandwidth filters using high-coupling SiO 2 /Y-X LiNbO 3. Jpn. J. Appl. Phys. 44,pp (2005). 5M. Kadota, et al. : Small surface acoustic wave duplexer for Wideband Code-Division Multiple Access full-band system having good temperature characteristics. Jpn. J. Appl. Phys. 46,pp (2007). 6R. Takayama, et al. : US-PCS SAW duplexer using high-q SAW resonator with SiO 2 coat for stabilizing temperature characteristics. Proc. IEEE Ultrason. Symp. pp (2004). 7T. Omori, et al. : Suppression of transverse mode responses in ultra-wideband SAW resonators fabricated on a Cu-grating/15 YX-LiNbO 3 structure. IEEE Trans. Ultrason., Ferroelec., and Freq. Contr. 54,pp (2007). 8R. Takayama, et al. : High power durable electrodes for GHz band SAW duplexers. Proc. IEEE Ultrason. Symp. pp.9-13 (2000).

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