Frequency stability of SAW oscillators at high temperatures

A broad overview is given of various factors affecting the frequency stability of surface-acoustic-wave (SAW) resonators. The objective has been to unravel the causes of large frequency drifts observed in SAW resonators operating at temperatures of 135 degrees C and beyond. Experimental data are presented on both the long-term and short-term frequency stabilities of SAW devices at 25 degrees C and 175 degrees C for moderate to high drive levels. The behavior of SAW devices with pure aluminum and copper-doped aluminum electrodes are compared. It is shown that the short-term frequency stability of SAW devices with copper-doped aluminum electrodes is a few parts in 10/sup 10/ even at 175 degrees C and for moderately large drive levels. Overall, the best short-term frequency stability is found to be for a gate time of 0.1 s.<
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