Patent ID: 6960866

Claim:
A surface acoustic wave device, comprising: a piezoelectric substrate; and at least two basic sections disposed on said piezoelectric substrate, each of the at least two basic sections including an asymmetrical double electrode defining a half wavelength section and having first and second strips with different widths from each other; wherein when edge positions of said first and second strips are X 1 , X 2 , X 3 and X 4 , each of which is a value corrected using a sonic speed difference between a free surface and a metallic surface, and when a resultant vector length of normalized reflected waves from the edge positions is |Γ|, and a center position of one of said at least two basic sections is 0(λ), and X 1 ≅−X 4 , each of the positions of X 2 and X 3 is substantially equal to a value satisfying the following equations (1) and (2): X 2 [λ]= A×X 1 [λ] 2 +B×X 1 [λ]+ C± 0.1[λ] (1) X 3 [λ]= D×X 1 [λ] 2 +E×X 1 [λ]+ F± 0.05[λ] (2); wherein in the equation (1) and (2), A to F are expressed by the following equations: A=− 34.546×|Γ| 6 +176.36×|Γ| 5 −354.19×|Γ| 4 +354.94×|Γ| 3 −160.44×|Γ| 2 +10.095×|Γ|−1.7558 B=− 15.464×|Γ| 6 +77.741×|Γ| 5 −153.44×|Γ| 4 +147.20×|Γ| 3 −68.363×|Γ| 2 +6.3925×|Γ|−1.7498 C=− 1.772×|Γ| 6 +8.7879×|Γ| 5 −17.07×|Γ| 4 +16.092×|Γ| 3 −7.4655×|Γ| 2 +0.8379×|Γ|−0.3318 D= 12 . 064 ×|Γ| 6 −45.501×|Γ| 5 +57.344×|Γ| 4 −22.683×|Γ| 3 +12.933×|Γ| 2 −15.938×|Γ|−0.1815 E= 7.2106×|Γ| 6 −30.023×|Γ| 5 +45.792×|Γ| 4 −29.784×|Γ| 3 +13.125×|Γ| 2 −6.3973×|Γ|+1.0203 F= 1.0138×|Γ| 6 −4.4422×|Γ| 5 +7.3402×|Γ| 4 −5.474×|Γ| 3 +2.3366×|Γ| 2 −0.7540×|Γ|+0.2637.