A switchable interdigital transducer in a SAW filter

摘要

The fingers 22 of a movable electrode of an interdigital transducer (IDT) lie in a cavity above the piezoelectric layer 12 and are moved down to contact the layer 12, between the fingers 14 of a fixed electrode, by applying voltages to electrostatic actuator electrodes 16 or 24. Alternatively, the movable fingers 22 may be formed just above the layer 12 and the actuators used to move the fingers away from the layer 12 or to apply a downward pull-in contact force. The technique allows the switching into circuit of SAW filters without incurring the insertion loss caused by FET switches, or a reduction in Q factor. A SAW filter arrangement may be set to a desired frequency by activating or deactivating selected SAW filters.