1.9-GHZ-BAND SURFACE-ACOUSTIC-WAVE DEVICE USING 2ND LEAKY MODE ON LITAO3

The propagation characteristics of a new high-phase-velocity leaky sur face acoustic wave (SAW) mode, which is called the second leaky mode, in a periodic structure on LiTaO3 (90 degrees, 90 degrees, 31 degrees) aere analyzed experimentally. The propagation loss is the lowest when the KH (K=wave number, H=Al electrode thickness) parameter is about 0 .5. The higher mode of the second leaky mode is excited when the KH pa rameter is larger than 0.7. A ladder type band-pass SAW filter utilizi ng the second leaky mode on LiTaO3 was designed and fabricated by appl ying the analysis results to the periodical structure. The pitch of th e electrode fingers is 0.8 mu m. The center frequency of the pass band is 1.938 GHz. The minimum insertion loss is 3.3 dB. The attenuation a t the center frequency +/-100 MHz is 25 dB. The measured characteristi cs of this filter can be sufficient for practical mobile communication systems.