Propagation of longitudinal leaky surface waves under periodicmetal grating structure on lithium tetraborate

摘要

The dispersion properties of longitudinal leaky surface wavesnpropagating under the periodic Al strip grating on lithium tetraboraten(Li2B4O7; LBO) are describedntheoretically and experimentally for applications of the mode to highnfrequency SAW devices. A theoretical method developed here is based onnFloquet's theorem using space harmonics as an orthogonal function setnand real boundary integral equations derived from the method of weightednresiduals for a period of each region, i.e., substrate, metal, and freenspace. The boundary integral equations are solved by using the Galerkinnprocedure. The periodic strip gratings with both single-electrodes andndouble-electrodes are investigated, considering the convergency of thennumerical computation for the number of the space harmonics. As anresult, the propagation loss for shorted gratings was found to benrelatively low in the thickness range of the Al strip below about 1% fornthe single-electrodes and 2% for the double-electrodes, although itngreatly increases for a thickness over 2% for the single-electrodes andn3% for the double-electrodes