Surface transverse wave (STW) resonator devices have been designed and fabricated on rotated Y cuts of quartz, with wave propagation perpendicular to the X axis. Packaged devices with center frequencies of 500 and 632 MHz show insertion loss less than 6 d B in a 50 ohm system. Unloaded Q is typically greater than 10,000. Devices at 1726 MHz show packaged insertion loss as low as 10 dB and unloaded Q as high as 5600. Temperature behavior was studied. STW resonators were found to exhibit significantly greater power-handling ability than SAW resonators with comparable design parameters and electrical performance in a comparison study. Device phase noise measurements indicate that STW resonators' noise improves when driven with high incident power. Single sideband device phase noise less than -135 dBc/Hz at 1 H z offset was achieved.

Novel Surface Transverse Wave Resonators with Low Loss and High Q

Recent Advances in Shallow Bulk Acoustic Wave Devices

A theoretical analysis of excitation, transmission, andreception of surface skimming bulk waves(SSBW)by a pair of interdigital electrodes on rotated Y-cut quartz has been performed. Because quartz is relatively weakly piezoelectric, solutions to the Christoffel equations decouple to first order into purely acoustic and electrostaticwaves. When a time-varying voltage is appliedto a set of interdigital electrodes, it is found that each Fourier component of the induced electrostatic potential is coupled to a phase-matched outward propagating acoustic plane wave through the requirementof zero normal surface stress. By integrating the acoustic power density overkspace, a simple analytical expression for the radiation resistanceis obtained in terms of the material and transducer parameters. An asymptotic integration of the Fourier-components of the acoustic wave amplitude leads through the method of saddle-point integration to a closed-form expression for acoustic wave amplitude and far-field radiation pattern. Reciprocity is used to obtain closed form expressions for insertionloss.

Excitation and Detection of Surface Skimming Bulk Waves on Rotated Y-Cut Quartz

https://ieeexplore.ieee.org/iel5/10277/32710/01533926.pdf

Further Investigation of Shallow Bulk Acoustic Waves Generated by Using Interdigital Transducers

Shallow bulk acoustic wave propagation in piezoelectric crystals is reviewed from the standpoint of work reported to date. It is compared to bulk and surface acoustic waves as to properties and device potential. Singly and doubly rotated cuts are considered, as are piezoelectric transduction energy trapping, equivalent networks, as well as areas of future work such as new materials other than quartz, and nonlinear effects.

K.F. Lau

Papers

Interdigital Transducers - A Means of Efficient Bulk Wave Excitation