PURPOSE: To improve the frequency temperature characteristics by setting different wavelengths and film thicknesses for the 1st and 2nd transducers connected in parallel on a piezoelectric substrate so as to obtain different frequency characteristics.

CONSTITUTION: The signals supplied from an oscillator 5 are resonated at the input parts at the sides of common electrodes 6-1 and 6-2 of the 1st transducer. This resonance output is selected to a specific frequency that is decided at the reception parts of common electrodes 6-3 and 6-4 according to the wavelength and the film thickness and delivered. So it with common electrodes 6-5 and 6-6 as well as 6-7 and 6-8 respectively. The frequency temperature characteristics of the 1st and 2nd transducers are set as shown in figures (a) and (b) by controlling the film thickness and the wavelength of each transducer. Then the integrated characteristics of (c) is obtained by connecting both transducers in parallel to each other. In other words, the frequency temperature characteristics can be improved compared with those of (a) and (b).