Surface acoustic wave devices for measuring water content in snow

Flood modeling programs rely heavily on headwater source data, such as snow water equiva- lence (SWE), to warn residents to evacuate and farmers to harvest. Harmonic transponders, which do not require a power source, are one solution for long-term measurement of SWE in the field. This work investigates the design of harmonic transponders using surface acoustic wave (SAW) devices to excite high-frequency signals from below the snowpack. Water will have a significant effect on frequencies in the low GHz range. Varying the substrate’s crys- tal cut angle and electrode configuration allows for the excitation of the necessary output frequency without submicron lithography.