Small-sized SAW duplexers with wide duplex gap on a SiO2/Al/LiNbO3 structure by using novel Rayleigh-mode spurious suppression technique

This paper describes the novel Rayleigh-mode spurious suppression technique for SAW duplexers with wide duplex gap on a SiO₂/Al/LiNbO₃ structure. We have cleared the optimum shape of SiO₂ with taking account of the difference of the electrode thickness. The shape of SiO₂ which can suppress the spurious depended on the thickness of Al electrode. By controlling the shape of SiO₂, the Rayleigh-mode spurious of both Band I and Band IV duplexers can be suppressed. The small-sized SAW duplexers for Band I and Band IV systems were realized by employing this technology and optimizing the thickness of Al electrode. Our duplexers show the excellent performances for actually use. Insertion loss of transmitting band for Band I and for Band IV are 1.2 dB and 1.3 dB. And, the TCF is about -30 ppm/degC. The size of these duplexers is 2.5 mm times 2.0 mm. Additionally, the duplexers have sufficient power durability by using the multi-layer electrodes of AlMgCu/Ti.