Surface acoustic wave resonator filter

Abstract

A surface acoustic wave resonator filter includes an interdigital electrode on a piezoelectric substrate and has a two-dimensional mode coupling structure coupling a longitudinal resonation in the longitudinal direction consistent with a propagating direction of a surface acoustic wave and a transversal mode resonation in a transverse direction perpendicular to the propagating direction.

What is claimed is:  
     
         1 . A surface acoustic wave resonator filter including an interdigital electrode on a piezoelectric substrate, having a two-dimensional mode coupling structure coupling a longitudinal resonation in the longitudinal direction consistent with a propagating direction of a surface acoustic wave and a transversal mode resonation in a transverse direction perpendicular to the propagating direction.  
     
     
         2 . A surface acoustic wave resonator filter as set forth in  claim 1 , wherein said two-dimensional coupling type structure is formed by proximately arranging first and second longitudinal mode coupling type resonators on said piezoelectric substrate for establishing transversal coupling.  
     
     
         3 . A surface acoustic wave resonator filter as set forth in  claim 2 , wherein each of said first and second longitudinal mode coupling type resonators is provided a plurality of resonance frequencies and one of the resonance frequencies of the first resonator is equal to one of the resonance frequencies of the second resonator.  
     
     
         4 . A surface acoustic wave resonator filter as set forth in  claim 3 , wherein the transversal mode coupling of the first and second longitudinal mode coupling type resonators is an acoustic coupling.  
     
     
         5 . A surface acoustic wave resonator filter as set forth in  claim 4 , wherein each of the first and second longitudinal mode coupling type resonators has a dummy electrode arranged adjacent own interdigital electrode in the longitudinal direction and adjacent to san interdigital electrode of the other resonator in the transverse direction for establishing the acoustic coupling.  
     
     
         6 . A surface acoustic wave resonator filter including an interdigital electrode on a piezoelectric substrate, comprising first and second longitudinal mode coupling type resonators utilizing longitudinal mode resonation in the longitudinal direction consistent with a propagating direction of a surface acoustic wave, said first and second longitudinal mode coupling type resonators being established a parallel connection between inputs and outputs thereof.  
     
     
         7 . A surface acoustic wave resonator filter as set forth in  claim 6 , wherein each of said first and second longitudinal mode coupling type resonators has first and second interdigital electrodes arranged adjacent to each other in the longitudinal direction, the first interdigital electrode of said first longitudinal mode coupling type resonator and the first interdigital electrode of said second longitudinal mode coupling type resonator are electrically connected, and the second interdigital electrode of said first longitudinal mode coupling type resonator and the second interdigital electrode of said second longitudinal mode coupling type resonator are electrically connected.  
     
     
         8 . A surface acoustic wave resonator filter as set forth in  claim 7 , respective of first interdigital electrodes and respective second interdigital electrodes of said first and second longitudinal mode coupling type resonators are used in the opposite polarities.  
     
     
         9 . A surface acoustic wave resonator filter as set forth in  claim 7 , wherein each space between the interdigital electrodes of said first and second longitudinal mode coupling type resonators are mutually shifted for a n/   2   wavelength (n is an odd integer).