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US 6,744,333 B2Granted
Surface acoustic wave filter device with balanced and unbalanced terminals
AssigneeMurata Manufacturing Co., Ltd.
InventorYoichi Sawada
Life of this patent
Estimating the term…
Abstract
A surface acoustic wave filter device includes a piezoelectric substrate, and first and second surface acoustic wave filter elements disposed on the piezoelectric substrate. Each of the surface acoustic wave filters has a plurality of IDTs disposed along the surface acoustic wave propagation direction. The first and second surface acoustic wave filter elements are arranged such that they are substantially equal in transmission amplitude characteristic within a band but different in transmission phase characteristic by about 180°. One end of each of the first and second surface acoustic wave filter elements define an unbalanced terminal, and the other end of each of the first and second surface acoustic wave filter elements define a balanced terminal.
Claims45
A surface acoustic wave filter device comprising:
- a piezoelectric substrate;
- and
- first and second surface acoustic wave filter elements disposed on said piezoelectric substrate;
- wherein
- said first surface acoustic wave filter element includes a plurality of IDTs disposed along the surface acoustic wave propagation direction;
- said second surface acoustic wave filter element includes a plurality of IDTs disposed along the surface acoustic wave propagation direction;
- said second surface acoustic wave filter element is arranged such that the transmission amplitude characteristic of said second surface acoustic wave filter element is substantially equal to that of said first surface acoustic wave filter element and such that the transmission phase characteristic of said second surface acoustic wave filter element is different by about 180° from that of said first surface acoustic wave filter element;
- one end of each of the first and second surface acoustic wave filter elements define unbalanced terminals and the other end of each of the first and second surface acoustic wave filter elements define balanced terminals;
- each of the first and second surface acoustic wave filter element has three IDTs and a second space defined in the second surface acoustic wave filter element between an IDT connected to the unbalanced terminal and an IDT connected to a balanced terminal is different by about 0.48λ to about 0.525λ from a first space defined in the first surface acoustic wave filter element between an IDT disposed at a central location and an IDT disposed on either side, where λ is the wavelength of the surface acoustic wave;
- and
- said first space is equal to about(n/2+1.22)×λ to about (n/2+1.33)×λ (n is an integer of 0 to 4), and said second space is equal to about (n/2+1.72)×λ to about (n/2+1.83)×λ (n is an integer of 0 to 4).
8 more elements
A surface acoustic wave filter device comprising:
- a piezoelectric substrate;
- and
- first and second surface acoustic wave filter elements disposed on said piezoelectric substrate;
- wherein
- said first surface acoustic wave filter element includes a plurality of IDTs disposed along the surface acoustic wave propagation direction;
- said second surface acoustic wave filter element includes a plurality of IDTs disposed along the surface acoustic wave propagation direction;
- said second surface acoustic wave filter element is arranged such that the transmission amplitude characteristic of said second surface acoustic wave filter element is substantially equal to that of said first surface acoustic wave filter element and such that the transmission phase characteristic of said second surface acoustic wave filter element is different by about 180° from that of said first surface acoustic wave filter element;
- one end of each of the first and second surface acoustic wave filter elements define unbalanced terminals and the other end of each of the first and second surface acoustic wave filter elements define balanced terminals;
- each of the first and second surface acoustic wave filter element has three IDTs and a second space defined in the second surface acoustic wave filter element between an IDT connected to the unbalanced terminal and an IDT connected to a balanced terminal is different by about 0.48λ to about 0.525λ from a first space defined in the first surface acoustic wave filter element between an IDT disposed at a central location and an IDT disposed on either side, where λ is the wavelength of the surface acoustic wave;
- and
- said first space is equal to about (n/2+1.22)×λ to about (n/2+1.33)×λ (n is an integer of 0 to 2), and said second space is equal to about (n/2+1.72)×λ to about (n/2+1.83)×λ (n is an integer of 0 to 2).
8 more elements
A surface acoustic wave filter device comprising:
- a piezoelectric substrate;
- and
- first and second surface acoustic wave filter elements disposed on said piezoelectric substrate;
- wherein
- said first surface acoustic wave filter element includes a plurality of IDTs disposed along the surface acoustic wave propagation direction;
- said second surface acoustic wave filter element includes a plurality of IDTs disposed along the surface acoustic wave propagation direction;
- said second surface acoustic wave filter element is arranged such that the transmission amplitude characteristic of said second surface acoustic wave filter element is substantially equal to that of said first surface acoustic wave filter element and such that the transmission phase characteristic of said second surface acoustic wave filter element is different by about 180° from that of said first surface acoustic wave filter element;
- one end of each of the first and second surface acoustic wave filter elements define unbalanced terminals and the other end of each of the first and second surface acoustic wave filter elements define balanced terminals;
- each of the first and second surface acoustic wave filter element has three IDTs and a second space defined in the second surface acoustic wave filter element between an IDT connected to the unbalanced terminal and an IDT connected to a balanced terminal is different by about 0.48λ to about 0.525λ from a first space defined in the first surface acoustic wave filter element between an IDT disposed at a central location and an IDT disposed on either side, where λ is the wavelength of the surface acoustic wave;
- and
- said first space is within the range from about 172λ to about 1.88λ and said second space is within the range from about 2.22λ to about 2.33λ.
8 more elements
Dependencies are inferred from the claim text.