SURFACE ACOUSTIC WAVE RESONATOR AND LADDER-TYPE SURFACE ACOUSTIC WAVE FILTER

摘要

PROBLEM TO BE SOLVED: To reduce ripples in a pass band and to improve flatness by providing a piezoelectric substrate and a driving electrode and first and second reflectors reflecting surface acoustic waves on both ends of the driving electrode on the piezoelectric substrate and varying the pitches of the first and second reflectors within the range of not more than a specified value. ;SOLUTION: In the SAW resonator, the IDT electrode 1 is formed on a lithium tantalate substrate and the reflectors 2 and 3 on both ends. An electric signal applied to IDT is emitted into the SAW lithium tantalate substrate of a wavelength adjusted to the pitch of the electrode finger of IDT. The SAW wave which is thus generated reciprocates between the reflectors 2 and 3 and generates a standing wave. The change rate of the right and left reflectors are set to be 0.1-1%. Since the frequencies subtly differ in generated spurious, they are mutually weakened while they reciprocate between the reflectors and ripple width is suppressed to be small to not more than about 0.05(dB).;COPYRIGHT: (C)1998,JPO