Applications of laser-trimming for all-quartz package, surface acoustic wave devices

Abstract

A laser-based technique that allows the frequency of sealed, all-quartz package (AQP) surface acoustic wave (SAW) resonators to be accurately set to within +or-1 p.p.m. of a prescribed frequency has previously been reported (J.A. Greer et al., 1987). SAW resonator devices in the range of 300 MHz to 1 GHz have been laser-trimmed by as much as 100 p.p.m. The laser-trimming process is extended to a variety of new applications, including accurately adjusting the insertion phase shift of AQP SAW delay lines by as much as 90 degrees ; effectively suppressing the distortion caused by the third-order transverse mode in resonators with nonapodized transducers, which usually results in improved insertion phase shift and insertion-loss responses for the device; and frequency trimming, used either to form accurately matched pairs of AQP SAW resonators for high-power applications by effectively doubling the acoustic aperture using two SAW resonators fabricated on the same substrate surface, or to form matched pairs of devices fabricated on opposite surfaces of the same substrate. The latter application is for high-vibration environments, reducing the combined vibration sensitivity due to the cancellation of strain-induced frequency shifts. The influence of laser-trimming on the residual flicker noise and long-term frequency stability of AQP SAW devices is discussed.