Spatial Thermal Gradient Effects on Precision MEMS Resonator Zero Rate Drift
Spatial thermal gradients shift MEMS zero rate drift by inducing asymmetric anchor stress, flexure mode coupling, and local frequency splitting.
Frequency Splitting
Resonant Phenomenon
Dual peaks appear in a vibrational spectrum when two identical oscillators interact through a shared mass or spring. This frequency splitting separates a single resonance into two distinct modes that move at different rates. One mode represents the oscillators moving in phase while the other represents them moving out of phase.
Mode Degeneracy
Symmetry in a micro-machined resonator usually keeps the operational frequencies of different axes identical. Small manufacturing errors or material grains cause frequency splitting that destroys this degeneracy. This separation is problematic for gyroscopes because it prevents the energy from transferring between the drive and sense axes efficiently.
Measurement Gap
Observation of the gap between the peaks is performed with a network analyzer. The frequency splitting is quantified in hertz or as a percentage of the center frequency. Engineers monitor this value during the manufacturing process to identify batches with excessive geometric variation.
Error Correction
Tuning the device involves adding or removing mass to bring the peaks closer together. Techniques like laser ablation or selective etching reduce frequency splitting to within the required bandwidth of the control electronics. If the split is too large, the phase shift becomes too steep for the feedback loop to track.
This adjustment is verified at the final stage of assembly.