| 摘要 |
PURPOSE:To prevent the in-band frequency characteristic of the titled device from being deteriorated due to a reflected wave by a capacitor by devising the titled device such that the direction of a reflected wave is largely and obliquely crossing to the propagating direction of the surface acoustic wave or the reflected waves are interfered mutually and cancelled together. CONSTITUTION:Electrodes or electrode fingers of a phase shifter in a direction nearly orthogonal to the propagation direction of a surface acoustic wave and reflecting the surface acoustic wave are tilted by an angle theta or over expressed in equation in a direction at a right angle to the surface acoustic wave propagation path. Or the width of electrodes or electrodes fingers forming a phase shifter on the substrate at nearly a right angle in the surface acoustic wave propagation direction is selected to an odd number of multiple of lambda/2 and the gap in the direction of the surface acoustic wave among those in parallel with each other and nearly at a right angle to the surface acoustic wave propagating direction or among ends in nearly parallel with the surface acoustic wave propagating direction is selected to be an odd number of multiple of lambda/4. Thus, adverse effect due to an undesired surface acoustic wave reflected on the electrode of a phase shift capacitor formed on the same piezoelectric substrate is suppressed.
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