| 摘要 |
PURPOSE:To reduce the size of a substrate of an elastic surface wave filter and to suppress the diffraction loss by setting an interdigital electrode so that an exciting source existing in the vicinity of another exciting source forming a maximum crossing width of other interdigital electrodes goes to zero. CONSTITUTION:Input/output side interdigital electrodes 21, 22 are formed on the elastic surface wave substrate 20 with a prescribed interval. The interdigital electrode 21 consists of interdigial electrodes 23, 24. The crossing width weighting is applied to the electrode 23 on the basis of an impulse response specifying an even number component, and an electrode section 23b of two common electrode sections 23a, 23b is formed so as to be placed nearly along with the envelope for weighting. The electrode 24 specifies an odd number component. After the electrode 24 is set in advance so that the exciting source positioned near the exciting source 23c forming the maximum crossing width of the electrode 23 goes to zero, the electrode 24 is formed at the non-crossing region of the even number component and on a propagating line of the other electrode 22. |
