Abstract
In this paper, we report a new structure of a shear horizontal (SH) type boundary acoustic wave for cellular phone applications. Such a structure composed of electrodes with a low shear wave velocity between two materials, namely, the SiO2 film/Au-electrode/LiNbO3 substrate, is proposed. The ladder filter used in this paper had this structure. By changing the propagation angle of the acoustic wave, the electromechanical coupling factor k2 range from 0 to 16% was obtained, as well as a normalized bandwidth range 0.67 to 1.85 fold as large as that of a 36–46°Y–X LiTaO3 leaky surface acoustic wave (LT-LSAW) filter. In addition, an excellent temperature coefficient of delay time (TCD=25 ppm/°C) and a large mutual coupling coefficient κ12 (=0.15) were also obtained.