PURPOSE: To suppress an undesired spurious level and crosstalk by forming two pairs of surface acoustic wave elements consisting of inter-digital converters and surface acoustic wave reflectors on a piezoelectric substrate to use one of both pairs as an oscillator and the other pair as an output filter respectively.

CONSTITUTION: The inter-digital converters 11 and 11 consisting of comb-tooth electrodes 11a and 11b crossing each other and surface acoustic wave reflectors 12 and 12 form a surface acoustic wave element A on a piezoelectric substrate 10 together with a surface acoustic wave element B. Then hot pins P1 and P2 of the element A are connected to an amplifier for formation of an oscillation circuit A. While an output filter circuit is formed by connecting the hot pins P3 and P4 of the element B to the output terminal of the circuit A and an output amplifier respectively. In such a constitution, the undesired spurious levels close to an oscillation frequency can be suppressed together with the higher harmonic wave distortions.