Abstract
The acoustic-surface-wave filter for the use of TV-intermediate frequency at 58 MHz was fabricated using an rf-sputtered ZnO film overlying the interdigital electrodes and the wave path on a glass substrate, and its fundamental properties for practical application were studied. The average and easily reproducible insertion loss characteristics are as follows: 16 dB at the minimum, 5(+16) dB at chromatic and picture signal carrier frequencies, 15(+16) dB at sound signal carrier frequency, more than 55(+16) dB at trap frequencies for adjacent channels, and 35(+16) dB at the maximum side lobe. The triple transit echo suppression is more than 35 dB. The temperature coefficient of the frequency characteristic is less than -30 ppm/°C. 500 days of aging has shown no significant change in the filter. Another type of filter for the use in U.S.A. is also fabricated by the same system.