Patent ID: 6580199
Filing Date: 2003-06-17
Classification: H03H

Abstract:
A surface acoustic wave apparatus equipped with an interdigital transducer that includes first and second common electrodes formed parallel on a piezoelectric substrate, a first split electrode group connected to the first common electrode and extending toward the second common electrode, and a second split electrode group connected to the second common electrode and extending toward the first common electrode; wherein:a plurality of pairs of electrode fingers that constitute the first split electrode group, and a plurality of pairs of electrode fingers that constitute the second split electrode group are interleaved at a cycle of &lgr;/2; each pair of electrode fingers includes a narrow-width electrode finger narrower than &lgr;/8 (&lgr; indicates a wavelength of a surface acoustic wave serving as an operation central frequency), and a wide-width electrode finger wider than &lgr;/8; a synthesized vector, obtained by synthesizing vectors of waves reflected from electrode fingers that are included within a distance of &lgr;/2 from any randomly-selected excitation point in a surface wave propagation direction, has a phase &PHgr; expressed by n&pgr;âˆ’5Â°&lE;&PHgr;&lE;n&pgr;+5Â° (n: a natural number) with respect to a phase of a wave excited by the interdigital transducer; and wherein a distance (t1) between centers of a randomly-selected electrode finger and one of the electrode fingers located at the opposite sides of the randomly-selected electrode finger, differs from a distance (t2) between centers of the randomly-selected electrode finger and the other of the electrode fingers located at the opposite sides of the randomly-selected electrode finger.