PURPOSE: To extract the designed frequency band width without attenuation while keeping an output level at its maximum level by employing Chebyshev impedance conversion circuit for a matching circuit connecting directly to a binary tree connecting to a rectangular output gate of a SAW(surface acoustic wave) convolver.

CONSTITUTION: A SAW device including a SAW convolver element which is provided with two input transducers 7, 8 on a piezoelectric substrate 17 and a rectangular output gate 9 between the input transducers has a binary tree 12 connecting to the output gate 9 with a bonding wire 16 and a matching circuit 14 being a Chebyshev type impedance conversion circuit connecting to the binary tree 12. The matching circuit 14 is a two-stage circuit connected in the order of parallel capacitors C0, C1, a series inductor L1,a parallel capacitor C2, and a series inductor L2, and includes an adjusting capacitor C3. The mismatching quantity of the matching circuit is decided in matching with the upper limit frequency of the design frequency band of the input transducers. Moreover, the mismatching quantity is selected to be minimized.