What is TC-SAW?

Schematic view of a typical TC-SAW stack

TC-SAW or Temperature Compensated Surface Acoustic Wave filter, as the name suggests, is SAW filter with improved thermal performance. The center frequency of a SAW filter is impacted considerably by variations in temperature. TC-SAW aims to provide higher performance in crowded RF spectrum by minimizing variations in the center frequency of the filter over temperature.

Standard SAW filters show a temperature-dependent frequency drift anywhere from -20 ppm/K up to -40 ppm/K, which makes them unsuitable for high-frequency applications and narrowband RF communication where the temperature can vary.

Frequency drift of a SAW filter as a function of temperature for non-compensated SAW filter and TC-SAW filter using silicon dioxide

In TC-SAW filters, a thin film of Silicon Dioxide (SiO2) is used to obtain good temperature coefficient of frequency (TCF). The application of silicon dioxide for temperature compensation reduces the temperature-dependent filter frequency drift and no significant drift is observed. It is worth noting that the filter performance strongly depends on the quality of the deposited SiO2 as it contributes to the acoustic wave propagation. For narrow band applications, the SiO2 thickness must be increased to achieve good TCF characteristics.

Click here to learn about SiO2 Think Film Technology for Temperature Compensated SAW Devices.