Temperature Compensation for Ball Surface Acoustic Wave Devices and Sensor Using Frequency Dispersion

We propose a new temperature compensation method for ball surface acoustic wave (SAW) devices using frequency dispersion. This method distinguishes the temperature effect independent of frequency and surface effects such as mass loading or elastic effects linearly dependent on frequency. After stating the principle of the method, we verify it by fabricating ball SAW devices with an interdigital transducer (IDT) that works at two frequencies, and apply them to the measurement of the coating of albumin on the surface of the device and on a hydrogen gas sensor with a surface-coated sensing film. Delay time measurements are carried out at two frequencies, and the difference in delay time is calculated to eliminate temperature-independent effects. Because the results clearly show surface effects without temperature disturbance, it is a difficult to realize sensors using ball SAW devices.