| 摘要 |
PURPOSE:To facilitate the generation of an electrode pattern by constituting the miniaturized forms of areas per unit length in driving electrodes and damping electrodes in such a way that the forms follow the non-linear function so that a side lobe becomes small in directional characteristics. CONSTITUTION:The electrode areas per unit length in the longitudinal direction of the driving electrodes 18 and 20 generated into area distribution which the areas gradually decrease corresponding to cos square curves towards both end parts with a central part in the longitudinal direction as an original. The electrode areas per unit length of the damping electrodes 22a, 22b, 24a and 24b are generated in areal distribution which they gradually decrease in proportion to (1-cos square) curves with directing the central part from both end parts in the longitudinal direction. Since respective electrodes can be printed and generated by a silk screen method, the forms of the electrodes can be set to appropriate to mass productivity while holding the accuracy of a curve form.
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