The temperature dependency of power leakage in LST-cut quartz Surface Acoustic Wave filters.

In a previous memorandum (54264-880822-01TM), the temperature performance of several Surface Acoustic Wave (SAW) filters made on ST- and LST-cut quartz were compared. It was reported that, in general, LST-cut devices showed better frequency and phase stability than that of the ST-cut devices. However, a greater insertion loss increase with increasing temperature was also observed for the LST-cut filters. We attributed this additional increase of insertion loss to an increase of power loss caused by leakage of the leaky wave. We also suggested that the trend of increasing insertion loss could be demonstrated theoretically. In a recent correspondence, Ken-ya Hashimoto of Chiba University in Japan confirmed our earlier assertion with detailed calculations. This memorandum reports this finding.