Surface acoustic wave resonator

摘要

A surface acoustic wave (SAW) resonator in which a pair of surface acoustic wave reflectors are spaced apart on a piezoelectric substrate from each other by a suitable distance and each consists of a grating electrode construction and a periodic array of grooves and a surface acoustic wave transducer which consists of an interdigital electrode structure and a periodic array of grooves is interposed between the reflectors and spaced apart therefrom by a suitable distance. The electrode period LT of the transducer and the electrode period LR of the reflectors are so selected as to satisfy the following equation: <IMAGE> +TR <IMAGE> where C1T: the acoustic mismatching term at the boundary between the electroded portion and the non-electroded portion of the transducer and is given by C1T=¦1-Z2/Z1¦/ pi where Z2: the acoustic impedance of the electroded portion, and Z1: the acoustic impedance of the non-electroded portion; C2T: the relative frequency decrease due to the periodic structure of the transducer; C2R: the relative frequency decrease due to the periodic structure of the reflector; and qT= pi C1TN where N is the number of electrode finger pairs in the transducer.