1.9-GHz-Band Surface Acoustic Wave Device Using Second Leaky Mode on LiTaO₃

Abstract

The propagation characteristics of a new high-phase-velocity leaky surface acoustic wave (SAW) mode, which is called the second leaky mode, in a periodic structure on LiTaO 3 (90°, 90°, 31°) aere analyzed experimentally. The propagation loss is the lowest when the K H ( K =wave number, H =Al electrode thickness) parameter is about 0.5. The higher mode of the second leaky mode is excited when the K H parameter is larger than 0.7. A ladder type band-pass SAW filter utilizing the second leaky mode on LiTaO 3 was designed and fabricated by applying the analysis results to the periodical structure. The pitch of the electrode fingers is 0.8 µ m. The center frequency of the pass band is 1.938 GHz. The minimum insertion loss is 3.3 dB. The attenuation at the center frequency ±100 MHz is 25 dB. The measured characteristics of this filter can be sufficient for practical mobile communication systems.