| 摘要 |
PURPOSE: To realize an excellent propagation characteristic by specifying a structure of piezoelectric resonator made of lithium tetraboride single crystal and having a couple of interdigital electrodes on the surface. CONSTITUTION: A couple of interdigital electrodes (input IDT 22 and output IDT 23) made of a metal whose major component is aluminum and whose interdigital electrode fingers are provided on the surface of a piezoelectric substrate 21 made of a lithium tetraboride single crystal. The cut angle of the surface of the piezoelectric substrate 21 and the propagation direction of a surface acoustic wave are selected to be 0-45 deg., 44-50 deg., 80-90 deg. and a range equivalent to them in the Euler's angle representation. Then a normalized film thickness h/λof the electrode by a wavelengthλof the surface acoustic wave is selected to be 0.029-0.097×(M/P)+0.082×(M/P)<2> <=(h/λ)<=0.033-0.059×(M/ P)+0.050×(M/P)<2> , whereλis the film thickness of the electrode, P is a period of electrode fingers and M is the width of the electrode fingers, and then the speed of the surface acoustic wave is more than the speed of the fast lateral wave of a bulk wave propagated in the same direction and no in excess of the speed of a longitudinal wave.
|
