| 摘要 |
PROBLEM TO BE SOLVED: To easily realize a surface acoustic wave filter, which uses a substrate having natural single-phase unidirectional transducer (NSPUDT) characteristics, especially, a cut langasite substrate showing excellent characteristics (0 deg., 140 deg., 22.5 deg. to 24 deg.), with a low cost. SOLUTION: In this surface acoustic wave device, a one-port surface acoustic wave resonator consisting of one interdigital transducer for surface acoustic wave excitation and a pair of grating reflectors between which this transducer is interposed is provided on a piezoelectric substrate. This piezoelectric substrate has NSPUDT characteristics different by electrode reflection characteristics in the forward direction (+ direction) and the reverse direction (- direction) of a surface acoustic wave, and GAP+≠GAP- is set where GAP+ is the distance between a grating reflector GR+ adjacent to the transducer in the + direction and the transducer and GAP- is the distance between a grating reflector GR- adjacent to the transducer in the - direction and the transducer.
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