Surface acoustic wave filter having unidirectional and bidirectional transducers
First Claim
Patent Images
1. A surface acoustic wave filter device comprising:
- a piezoelectric substrate;
an input side transducer formed on said substrate, for exciting a surface acoustic wave;
an output side transducer formed on said substrate, for receiving and converting the surface acoustic wave excited by said input side transducer;
one of said transducers comprising a unidirectional transducer and the other of said transducers comprising a bidirectional transducer,wherein said unidirectional transducer comprises at least one electrode comprising a plurality of sets of first and second electrode fingers, said sets of electrode fingers being periodically arranged at a pitch λ
which is the propagation wavelength of said surface acoustic wave, said first electrode finger having a width λ
/8, said second electrode finger having a width 3λ
/8, and said first and second electrode fingers being spaced from each other at a center distance 3λ
/8;
wherein said bidirectional transducer comprises electrode fingers of a split-structure, said electrode fingers of the bidirectional transducer each having a width λ
/8; and
wherein said unidirectional transducer comprises a normal electrode and said bidirectional transducer comprises a weighted electrode.
0 Assignments
0 Petitions
Accused Products
Abstract
A surface acoustic wave filter device suitable for CDMA communication system includes a piezoelectric substrate, and a unidirectional input side transducer and a bidirectional output side transducer are formed on the substrate. The filter device has satisfactory filtering characteristics in terms of insertion loss, frequency characteristic, T.T.E. attenuation level, group delay time, etc.
-
Citations
3 Claims
-
1. A surface acoustic wave filter device comprising:
-
a piezoelectric substrate; an input side transducer formed on said substrate, for exciting a surface acoustic wave; an output side transducer formed on said substrate, for receiving and converting the surface acoustic wave excited by said input side transducer; one of said transducers comprising a unidirectional transducer and the other of said transducers comprising a bidirectional transducer, wherein said unidirectional transducer comprises at least one electrode comprising a plurality of sets of first and second electrode fingers, said sets of electrode fingers being periodically arranged at a pitch λ
which is the propagation wavelength of said surface acoustic wave, said first electrode finger having a width λ
/8, said second electrode finger having a width 3λ
/8, and said first and second electrode fingers being spaced from each other at a center distance 3λ
/8;wherein said bidirectional transducer comprises electrode fingers of a split-structure, said electrode fingers of the bidirectional transducer each having a width λ
/8; andwherein said unidirectional transducer comprises a normal electrode and said bidirectional transducer comprises a weighted electrode.
-
-
2. A surface acoustic wave filter device comprising:
-
a piezoelectric substrate; an input side transducer formed on said substrate, for exciting a surface acoustic wave;
an output side transducer formed on said substrate, for receiving and converting the surface acoustic wave excited by said input side transducer;one of said transducers comprising a unidirectional transducer and the other of said transducers comprising a bidirectional transducer, wherein said unidirectional transducer comprises a first electrode which comprises a plurality of sets of first and second electrode fingers, which sets are periodically arranged at a predetermined pitch, said first and second electrode fingers of each set having a width λ
/4 as measured in the propagation direction of the surface acoustic wave, where λ
is the propagation wavelength of said surface acoustic wave, and one of said set of electrode finders is spaced from the other by a center distance λ
;
a second electrode comprising a plurality of electrode fingers each arranged between the first and second electrode fingers of each set of said first electrode, and having a width λ
/4; and
at least one floating electrode arranged between opposite first and second electrode fingers of adjacent sets of said first electrode and having a width λ
/4; andwherein said bidirectional transducer comprises electrode fingers of a split-structure, said electrode fingers of the bidirectional transducer each having a width λ
/8.
-
-
3. A surface acoustic wave filter device comprising:
-
A) a piezoelectric substrate; B) an input side transducer formed on said substrate, for exciting a surface acoustic wave; and C) an output side transducer formed on said substrate, for receiving and converting the surface acoustic wave excited by said input side transducer; D) one of said transducers comprising a unidirectional transducer and the other of said transducers comprising a bidirectional transducer, wherein said unidirectional transducer comprises; i) a first electrode comprising a plurality of sets of electrode fingers arranged at a predetermined pitch, each of said sets of the first electrode comprising first, second, third and fourth electrode fingers each having a width λ
/8 as measured in the propagation direction of the surface acoustic wave, where λ
is the propagation wavelength of said surface acoustic wave, said first and second electrode fingers of each set being spaced from each other by a center distance λ
/4, said second and third electrode fingers of each set being spaced from each other by a center distance 3λ
/4, and said third and fourth electrode fingers of each set being spaced from each other by a center distance λ
/4;ii) a second electrode comprising a plurality of sets of electrode fingers arranged at a predetermined pitch, each of said sets of the second electrode comprising fifth and sixth electrode fingers each having a width λ
/8 as measured in the propagation direction of the surface acoustic wave, said fifth and sixth electrode fingers of each set being spaced from each other by a center distance λ
/4 and arranged between the second and third electrode fingers of an adjacent set of the first electrode; andiii) at least one floating electrode having a width λ
/4 as measured in the propagation direction of the surface acoustic wave and arranged between neighboring sets of electrode fingers of the first electrode.
-
Specification