| 摘要 |
PURPOSE:To improve the insertion loss and the characteristic by constituting the exciting section with the 1st and 2nd exciting section arranged in the broadwise direction of a piezoelectric ceramic at an interval of nlambda+l/4 and propagating the bulk wave excited by the 1st exciting section into a direction opposite to the 2nd exciting section only. CONSTITUTION:The exciting section of a bulk wave filter 11 consists of the 1st exciting section 17a and the 2nd exciting section 17b and they are arranged with plural internal electrodes 13a-13d and 13e-13i respectively. The electrodes 13a-13d and 13e-13i are led out to external electrodes 15a, 15b, 15c formed at both end faces of the piezoelectric ceramic 12 respectively. Furher, a coil 19 is connected between the external electrodes 15a and 15c of the exciting section 17b so that the bulk wave propagated from the exciting section 17a is reflected at the exciting section 17b efficiently. The exciting sections 17a and 17b are arranged by providing the interval of nlambda+lambda/4 in the broadwise direction of the ceramic 12 so as to propagate the bulk wave excited by the exciting section 17a in the direction opposite to the exciting section 17b only thereby improving the insertion loss. |
