Environmentally-robust high-performance tri-axial bulk acoustic wave gyroscopes

This paper reports on the design and characterization of the first commercially-available tri-axial rotation-rate sensor implemented by the use of substrate-decoupled bulk acoustic wave (SD-BAW) gyroscopes. Owed to their high-frequency of operation (4.3 MHz), these devices exhibit significantly reduced dependencies on environmental stimuli such as vibration and shock. The sensor consists of three separate, but identical, wafer-level packaged (WLP) gyros, each of which is oriented along the X, Y and Z axes for 3-axis detection. The three gyro dies are co-integrated in a 7 mm × 7 mm × 2.9 mm cavity package with an application specific integrated circuit (ASIC) responsible for signal actuation, readout, control of the device. With a scale factor of 3 mV/(°/s), the complete system attains a full-scale range (±300 °/s) with non-linearity of 0.05%. Furthermore, integration of all dies in the same package facilitates achieving low cross-axis sensitivity of less than 1%. Values as low as 0.17 °/√h of angle-random walk (ARW) and 10.5 °/h of bias-instability (BI) have been measured; these are dominated by the thermal and 1/f noise of the ASIC, respectively.