Ring waveguide resonator on SAW - quality factor vs electrode structure properties

A recently proposed new regular electrode structure named as ring waveguide resonator (RWR) on surface acoustic waves (SAW) is investigated. The structure consists of an interdigital transducer in the form of a ring placed on the Z-cut of a hexagonal piezoelectric crystal. Finite thickness electrodes produce the known slowing effect for a SAW in comparison with this SAW on a free surface. The ldquoslowrdquo electrode region and the ldquofastrdquo surrounding region form a waveguide with the acoustic field concentrated mainly in the electrode region. Due to its regularity the electrical admittance of RWR does not have sidelobes, which are typical for usual SAW resonators composed of different electrode gratings with gaps. SAW in a ring waveguide loses its energy due to radiation into the surrounding region. The resonator quality factor corresponding to such radiation losses can be drastically increased both by increasing of the waveguide radius and by improvement of the slowing properties of electrode structure.