JPS63110809A - Surface acoustic wave propagation element - Google Patents

Abstract

PURPOSE:To attenuate or remove an unnecessary reflected wave and to improve performance by differing an input interdigital electrode, an output interdigital electrode and widths of their dummy electrodes. CONSTITUTION:Such constitution is adapted that the crossing tooth width alphaof the cross part of the input interdigital electrode 6 is different from the crossing tooth width beta of the dummies of the input interdigital electrode 6 and output interdigital electrode 7. As a result reflection signals from the dummy electrodes are substantially reduced to enhance the performance of an elastic surface wave propagation element. Thus the elastic surface wave propagation element can be offered which has few unnecessary reflected waves and an excellent element characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a surface acoustic wave propagation element whose performance is improved by attenuating and removing unnecessary reflected waves.

BACKGROUND OF THE INVENTION A conventional surface acoustic wave propagation element will be explained. In Fig. 3, 1 is a piezoelectric substrate, 2 is a weighted comb-shaped electrode for generating or receiving surface acoustic waves, 3 is a regular comb-shaped electrode for generating or receiving surface acoustic waves, and 4 is a weighted comb-shaped electrode. It is known that in a surface acoustic wave propagation device in which the surface acoustic wave propagation velocity within the comb-shaped electrode is made uniform, an unnecessary reflected signal from the dummy electrode 4 is present, which significantly deteriorates the device characteristics.

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface acoustic wave propagation device that eliminates the above-mentioned drawbacks and has good device characteristics with few unnecessary reflected waves.

Means for Solving Problems The key point of the present invention is the comb width of the weighted comb-shaped electrode.Examples of the surface acoustic wave propagation element of the present invention will be described below with reference to the drawings.

FIG. 1 is a top view of a surface acoustic wave propagation element produced according to the present invention. In the figure, 5 is a lithium tantalate single crystal, 6 is an input comb-shaped electrode that generates surface acoustic waves, and 7 is an output comb-shaped electrode that converts the surface acoustic waves into electrical signals. Further, α is the width of the comb teeth of the intersecting portion of the input comb-shaped electrode 6, and β is the width of the comb teeth of the dummy portion of the input comb-shaped electrode 6.

FIG. 2 is a characteristic diagram showing the relationship between the relative value of the unnecessary reflected signal level from the dummy electrode (the relative value when α=β) and the ratio of α and β.

When the surface acoustic wave propagation device according to the present invention was operated in the 36 MHz band, the level of unnecessary reflected signals from the dummy electrode decreased by about 16 cm when the ratio of α and β was around 1·θ, and good results were obtained. Obtained.

Effects of the Invention As described above, according to the present invention, reflected signals from dummy electrodes are significantly suppressed, and the contribution to improving the performance of surface acoustic wave propagation elements is extremely large.

[Brief explanation of the drawing]

Fig. 1 is a top view showing the configuration of a surface acoustic wave propagation element according to an embodiment of the present invention, and Fig. 2 shows the effects of the present invention. FIG. 3 is a top view showing a conventional surface acoustic wave propagation element. 6...Lithium tantalate single crystal, 6...
...Input comb-shaped electrode, Output comb-shaped electrode,
α・・・・・・Comb tooth width of the intersection part of the input comb tooth shaped electrode, β
・・・・・・Comb tooth width of part of input comb tooth electrode
1. The detailed stele of Narim, which is in the 1st ward, also works, Figure 2 I, u 12/, 4/, 6 l, ? lA Figure 3

Claims (1)

[Claims] In a surface acoustic wave propagation element having an input comb-shaped electrode and an output comb-shaped electrode at a predetermined interval on the surface of a piezoelectric substrate, the input comb-shaped electrode and the output comb-shaped electrode and their dummy electrodes have different electrode widths. A surface acoustic wave propagation device characterized by: