| 摘要 |
PURPOSE:To improve the deterioration of the characteristic of a block region due to the decrease in impedance at high frequencies by arranging at least >=2 stages of electrodes. CONSTITUTION:The electrodes shown in hatched lines are formed as three-stage (n=3) structure. The electrodes are connected in series electrically by the capacitance between the stages and connected in parallel acoustically because the propagation path of an elastic wave between respective stages is in parallel. While the impedance at regions except in the vicinity of the resonance point is expressed as ZA' 1/jomegaCd' (Cd' is a damping capacitance), the impedance is ZA' n/jomegaCd' with the electrodes of n-stage structure. Thus, the impedance of the Cd' is increased to n times, the impedance is kept large thereby improving the characteristic improvement of the block region. |
