| 摘要 |
PURPOSE:To decrease the capacitance ratio and to increase the Q at anti- resonance point by selecting the number of teeth and the film thickness of an interdigital grating reflector so that the resonance frequency is arranged to a stop band lower limit frequency of the reflecting characteristic of the grating reflector and the anti-resonance frequency is arranged to the upper limit frequency. CONSTITUTION:The structure of the resonator is of one terminal pair type, an LiTaO3 36 deg. rotating Y board of a piezoelectric substrate 1 is used, an interdigital electrode 2 (20 pairs) made of an aluminum thin film of 0.1mum thickness is provided, and then the grating reflectors 3, 4 where 200 each stops of 1.0mum of line width being 1/4 of the surface acoustic wavelength are arranged at an interval of 1/2 wavelength at both sides are provided. Since the number of the teeth of the interdigital electrode 2 and the grating reflectors 3, 4 and the aluminum film thickness are selected so that the resonance frequency fr is arranged at the left shoulder and the anti-resonance frequency fa is arranged at the right shoulder, although the loss at the resonance frequency is decreased slightly, the width of the anti-resonance Q and the width of the resonance versus anti-resonance frequency is improved. |
