Patent ID: 6937116
Filing Date: 2005-08-30
Classification: H03H

Abstract:
1. A resonance type of longitudinal double-mode SAW filter including a piezoelectric plate, comprising: a first interdigital transducer that generates surface acoustic waves; a second interdigital transducer that receives the surface acoustic waves that are generated by said first interdigital transducer; a third interdigital transducer that is disposed between said first interdigital transducer and said second interdigital transducer that controls an amplitude of the surface acoustic waves that are generated; and a pair of reflectors on disposed both sides of said first, second and third interdigital transducers in a direction in which said surface acoustic waves propagate (longitudinal direction X), said reflectors and said first, second and third interdigital transducers being formed by periodically arranging metallic parallel conductors on said piezoelectric plate, and a distance between a closest parallel conductor among said reflectors and said first and second interdigital transducers, being equal to a space or (one periodic length+space) between a line and the space possessed by one period of the interdigital transducers, and an intersecting conductor and wherein, if the wavelength of the surface acoustic waves is defined by λ and n is an integer of 0, 1, 2, - - - , then, total lengths D and the lengths PT nearly all of higher-order natural mode oscillation displacements A