SURFACE ACOUSTIC WAVE DEVICE

PURPOSE:To obtain a required characteristic by taking a coordinate difference in a direction at a right angle to the surface acoustic wave propagating direction of two pairs of interdigital electrodes adjacent to weighted electrodes as 1/2 of the vector sum of two interdigital electrode pair delta oscillating sources so as to suppress spurious surface acoustic wave. CONSTITUTION:A surface acoustic wave element for FM reproduction phase equalizer of a VTR is used as an example of execution and a video frequency is frequency-converted into 14MHz. A lithium niobate single crystal having a plate thickness of 0.5mm., 128 deg. rotation Y axis cut X propagation is used as a piezoelectric substrate 9. An input electrode 10 is 3.5 pairs of normal electrodes and an output electrode 11 is a weighted electrode of 7.5 pairs of double electrode structure. Aluminum vapor-deposition film having a thickness of 8,000Angstrom is formed to the electrodes by the photolithography technology. The aperture length of the electrode fingers is 1,890mum and the gap with a dummy electrode finger is 50mum.