Phase velocity control of surface acoustic waves based on surface shorting and electrical field application using MEMS switches

We have investigated controlling the phase velocity of a surface acoustic wave (SAW) by a microelectromechanical switch fabricated on a high coupling piezoelectric substrate. The principle is based on the interaction of the evanescent surface potential of the SAW with the conductive switch. In theory tuning of the velocity in the range given by v(0) and v(m), i.e. the velocity for a SAW on a free and metallized substrate, is possible. We have achieved up to 17.6 m/s (0.44 %) velocity tuning on 128 degrees YX LiNbO3. A maximum velocity sensitivity of Delta v/v of 15x10(-3)/V and phase sensitivity of 700 degrees/V was measured. This is five orders of magnitude larger than values obtained for electrical field tuning.