Dynamic and static pressure sensitivities of AQP SAW oscillators

The dynamic and static pressure sensitivities of two “all quartz package” (AQP) surface acoustic wave (SAW) hybrid circuit oscillators, one at 375 MHz and one at 935 MHz, have been evaluated. Dynamic pressure sensitivity measurements were made from 50 Hz to 7 kHz, with pressure levels ranging from 20 to 500 Pa. For the static pressure sensitivity measurements, the pressure varied over the range from zero to two atmospheres in one atmosphere steps. Considerable care was taken in the measurement procedures to identify and minimize the effects of other competing environmental factors such as vibration and temperature changes. The oscillators were tested both with and without alumina stiffeners on the hybrid package´s base and cover. The observed dynamic pressure sensitivity at 50 Hz agreed with the static pressure sensitivity within approximately a factor of three or four. The measured dynamic pressure sensitivities were in the range of 1×10^-13 to 6×10^-12 fractional frequency change per Pa, while the measured static pressure sensitivities were on the order of 1×10^-13 fractional frequency change per Pa. Details of the measurement techniques are included and the results described