INTERDIGITAL TRANSDUCER AND SURFACE ACOUSTIC WAVE FILTER

PURPOSE:To obtain the same reflected wave cancelling effect as the double electrode type by applying an absorbent on a specific part of partial electrodes where internal reflect occurs out of plural electrodes and absorbing the surface acoustic wave propagated from another electrode by this absorbent. CONSTITUTION:An absorbent 1 is applied on the part where internal reflection occurs, for example, the electrode part in a range of oblique lines of an apodize electrode group 10, and electrode oscillation due to a reflected wave is suppressed by the absorbent 1. High polymer materials like silicone rubber or a non-volatile adhesive is used as the absorbent 1, and its application quantity is a minimum required for suppression of electrode oscillation. Therefore, electrode oscillation due to the surface acoustic wave propagated in the direction opposite to the direction of an arrow is suppressed by the absorbent 1 when a voltage is applied to the electrode group 10. Consequently, internal reflection is relaxed, and the same reflected wave cancelling effect as a double electrode type comb shaped type electrodes (IDT) is realized with the single type electrode group (apodize electrode group).