Microphonic sensitivity of surface-acoustic-wave resonators

The shift in resonant frequency due to acceleration has been measured for surface-acoustic-wave resonators (SAWRs). SAWR devices were subjected to vibration from 5 Hz to 10 kHz with peak accelerations ranging from 10(-2) to 10(3) g. The vibration was applied both normal to and in the plane of propagating surface wave yielding microphonic sensitivities on the order of 1 ppb/g. To confirm the results of the direct measurement method, an oscillator loop was closed around the vibrated SAWR and the magnitudes of the FM sidebands were measured to indicate the resulting frequency shift. Several bulk crystal resonators were also measured and it was found that the microphonic sensitivities were generally comparable in magnitude to those of the SAWRs but spanned much wider ranges.