SURFACE ACOUSTIC WAVE DEVICE

摘要

PURPOSE:To set the number of taps to an optimum value and to reduce the end defect peculiar to surface acoustic waves by weighting a Fourier-transformed main pulse response wave with lengths of electrode crossing fingers of a surface acoustic wave transformer and forming the inter-electrode pitch with an equal interval part and an unequal interval part. CONSTITUTION:Electrodes of transmissin-side and reception-side surface acoustic wave transformer 11 and 12 perform Fourier transform of a desired amplitude characteristic and are weighted with lengths of crossing fingers. Pairs of electrodes 11b and 11c and electrodes 12b and 12c in the outermost parts corresponding to the part of the second side lobe out of these arranged electrodes are arranged at pitch intervals different from those of electrodes in the other parts 11a and 12a. These pairs of electrodes 11b and 11c and electrodes 12b and 12c are subjected to what is called phase weighting. Thus, electrodes in the outermost parts of transformer have a regular electrode structure to suppress the generation of unnecessary waves.