Microphonic sensitivity of surface-acoustic-wave resonators

Area of Science:

• Physics
• Materials Science
• Electrical Engineering

Background:

• Surface-acoustic-wave resonators (SAWRs) are sensitive to external stimuli.
• Acceleration can induce unwanted frequency shifts in resonators, impacting device performance.
• Understanding and quantifying the microphonic effect in SAWRs is crucial for high-precision applications.

Purpose of the Study:

• To measure the resonant frequency shift in SAWRs caused by acceleration.
• To quantify the microphonic sensitivity of SAWRs under various vibration conditions.
• To compare the microphonic behavior of SAWRs with traditional bulk crystal resonators.

Main Methods:

• SAWR devices were vibrated across a frequency range of 5 Hz to 10 kHz with accelerations from 10⁻² to 10³ g.
• Vibration was applied both normal to and in the plane of the surface acoustic wave propagation.
• An oscillator loop was used to confirm direct measurements by analyzing FM sidebands.

Main Results:

• SAWRs demonstrated microphonic sensitivities on the order of 1 part per billion per g (ppb/g).
• The measured frequency shifts were consistent across different vibration orientations.
• Bulk crystal resonators showed comparable microphonic sensitivities but with a significantly wider range.

Conclusions:

• SAWRs possess measurable microphonic sensitivities, indicating susceptibility to acceleration-induced frequency shifts.
• The direct measurement and oscillator loop methods provide reliable quantification of this effect.
• SAWRs offer a viable alternative to bulk crystal resonators in applications where microphonic noise is a concern.