PURPOSE: To obtain a small-capacity and programable filter by securing the propagation parallel to the direction of the cross-finger electrode and then linking the electrode of the wave receiving converter to each cross-finger electrode via the switch region.

CONSTITUTION: Reflective grid 3 is formed by arraying in the propagating direction the several units of reflectors which are distributed with the 45° angle to the propagating direction of the elastic surface wave generated from wave transmitting converter 2 and with the pitch space changing continuously. Then wave receiving converter 4 in which the pitch of cross-finger electrode 9 varies continuously is installed to secure the angle of 45° to the arrangement direction of grid 3 and furthermore with the direction of electrode 9 set parallel to the propagating direction. Then electrode 8 of one side of converter 4 is linked to its each electrode 9 via switch region 7. In such way, a samll-capacity and programable filter can be obtained.