US 5,874,868 AGranted

Longitudinally coupled surface acoustic wave resonator filter having different distances between transducers

AssigneeMurata Manufacturing Co., Ltd.

InventorKazunobu Shimoe

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Abstract

A longitudinal coupling type SAW resonator filter achieves improved selectivity without increasing the insertion loss and is constructed so as to be more easily mass-produced. The longitudinal coupling type SAW resonator filter has a piezoelectric substrate and first, second and third sets of interdigital electrodes each including a pair of comb electrodes disposed on the piezoelectric substrate. A pair of reflectors are located on the opposite sides in the surface wave propagation direction of the area in which the first to third sets of interdigital electrodes are disposed. The distance between the centers of adjacent electrode fingers of the first and second sets of interdigital electrode and the distance between the centers of adjacent electrode fingers of the first and third sets of interdigital electrode are set to different values.

Claims10

Dependent claims

A longitudinally coupled surface acoustic wave resonator filter comprising:

a substrate;
first, second and third interdigital transducers disposed on a surface of said substrate;
said second and third interdigital transducers being located on opposite sides of said first interdigital transducer in a direction of propagation of surface waves excited and received by said first interdigital transducer;
first and second reflectors located on said substrate at opposite ends of an area in which said first, second and third interdigital transducers are provided;
each of said first, second and third interdigital transducers including a pair of comb electrodes each having at least one electrode finger;
and
a distance L.sub.1 between centers of the at least one electrode finger of said first interdigital transducer and the at least one electrode finger of said second interdigital transducer located adjacent to each other and a distance L.sub.2 between centers of the at least one electrode finger of said first interdigital transducer and the at least one electrode finger of said third interdigital transducer located adjacent to each other being set to different values;
wherein
each of said first and second reflectors has a plurality of electrode fingers arranged substantially perpendicularly to the surface wave propagation direction, a wavelength of surface waves determined by an electrode pitch of the reflectors is .lambda. and said distance L.sub.1 satisfies an inequality (1):
0+n.lambda..ltoreq.L.sub.1 .ltoreq..lambda./2+n.lambda. (1)
(n:
an integer)
said distance L.sub.2 satisfies an inequality (2):
.lambda./2+m.lambda..ltoreq.L.sub.2 .ltoreq.(m+1).lambda. (2)
(m:
an integer)
said distance L.sub.1 and L.sub.2 satisfy an inequality (3):
L.sub.1 .noteq.L.sub.2 -.lambda./2+k.lambda. (3)
(k:
an integer).

17 more elements

A double mode filter comprising:

a longitudinally coupled surface acoustic wave resonator filter including first, second and third interdigital transducers disposed on a surface of said substrate, said second and third interdigital transducers being located on opposite sides of said first interdigital transducer in a direction of propagation of surface waves excited and received by said first interdigital transducer, first and second reflectors located on said substrate at opposite ends of an area in which said first, second and third interdigital transducers are provided, each of said first, second and third interdigital transducers including a pair of comb electrodes each having at least one electrode finger, and a distance L.sub.1 between centers of the at least one electrode finger of said first of interdigital transducer and the at least one electrode finger of said second interdigital transducer located adjacent to each other and a distance L.sub.2 between centers of the at least one electrode finger of said first interdigital transducer and the at least one electrode finger of said third interdigital transducer located adjacent to each other being set to different values;
wherein each of said first and second reflectors has a plurality of electrode fingers arranged substantially perpendicularly to the surface wave propagation direction, a wavelength of surface waves determined by an electrode pitch of the reflectors is .lambda. and said distance L.sub.1 satisfies a relationship (1):
0+n.lambda..ltoreq.L.sub.1 .ltoreq..lambda./2+n.lambda. (1)
(for any value of n where n is an integer)
said distance L.sub.2 satisfies a relationship (2):
.lambda./2+m.lambda..ltoreq.L.sub.2 .ltoreq.(m+1).lambda. (2)
(for any value of m where m is an integer)
said distances L.sub.1 and L.sub.2 do not satisfy a relationship (3):
L.sub.1 =L.sub.2 -.lambda./2+k.lambda. (3)
(for all values of k where k is any integer)
such that two resonant modes are defined in the double mode filter;
at least one of a longitudinally coupled surface acoustic wave resonator filter, a transversely coupled surface acoustic wave resonator filter and a trap filter including a surface acoustic wave resonator disposed on the substrate and electrically connected to said longitudinally coupled surface acoustic wave resonator filter.

9 more elements

An electronic component comprising:

a substrate;
a plurality of longitudinally coupled surface acoustic wave resonator filters located on said substrate and connected in series to each other, each of said plurality longitudinally coupled surface acoustic wave filters including:
first, second and third interdigital transducers disposed on a surface of said substrate;
said second and third interdigital transducers being located on opposite sides of said first interdigital transducer in a direction of propagation of surface waves excited and received by said first interdigital transducer;
first and second reflectors located on said substrate at opposite ends of an area in which said first, second and third interdigital transducers are provided;
each of said first, second and third interdigital transducers including a pair of comb electrodes each having at least one electrode finger;
and
a distance L.sub.1 between centers of the at least one electrode finger of said first interdigital transducer and the at least one electrode finger of said second interdigital transducer located adjacent to each other and a distance L.sub.2 between centers of the at least one electrode finger of said first interdigital transducer and the at least one electrode finger of said third interdigital transducer located adjacent to each other being set to different values;
wherein
each of said first and second reflectors has a plurality of electrode fingers arranged substantially perpendicularly to the surface wave propagation direction, a wavelength of surface waves determined by an electrode pitch of the reflectors is .lambda. and said distance L.sub.1 satisfies an inequality (1):
0+n.lambda..ltoreq.L.sub.1 .ltoreq..lambda./2+n.lambda. (1)
(n:
an integer)
said distance L.sub.2 satisfies an inequality (2):
.lambda./2+m.lambda..ltoreq.L.sub.2 .ltoreq.(m+1).lambda. (2)
(m:
an integer)
said distance L.sub.1 and L.sub.2 satisfy an inequality (3):
L.sub.1 .noteq.L.sub.2 -.lambda./2+k.lambda. (3)
(k:
an integer).

18 more elements

A surface acoustic wave resonator filter device comprising:

a longitudinally coupled surface acoustic wave resonator filter including first, second and third interdigital transducers disposed on a surface of said substrate, said second and third interdigital transducers being located on opposite sides of said first interdigital transducer in a direction of propagation of surface waves excited and received by said first interdigital transducer, first and second reflectors located on said substrate at opposite ends of an area in which said first, second and third interdigital transducers are provided, each of said first, second and third interdigital transducers including a pair of comb electrodes each having at least one electrode finger and a distance L.sub.1 between centers of the at least one electrode finger of said first interdigital transducer and the at least one electrode finger of said second interdigital transducer located adjacent to each other and a distance L.sub.2 between centers of the at least one electrode finger of said first interdigital transducer and the at least one electrode finger of said third interdigital transducer located adjacent to each other being set to different values;
wherein each of said first and second reflectors has a plurality of electrode fingers arranged substantially perpendicularly to the surface wave propagation direction, a wavelength of surface waves determined by an electrode pitch of the reflectors is .lambda. and said distance L.sub.1 satisfies an inequality (1):
0+n.lambda..ltoreq.L.sub.1 .ltoreq..lambda./2+n.lambda. (1)
(n:
an integer)
said distance L.sub.2 satisfies an inequality (2):
.lambda./2+m.lambda..ltoreq.L.sub.2 .ltoreq.(m+1).lambda. (2)
(m:
an integer)
said distance L.sub.1 and L.sub.2 satisfy an inequality (3):
L.sub.1 .noteq.L.sub.2 -.lambda./2+k.lambda. (3)
(k:
an integer);
and
at least one of a longitudinally coupled surface acoustic wave resonator filter, a transversely coupled surface acoustic wave resonator filter and a trap filter including a surface acoustic wave resonator disposed on the substrate and electrically connected to said longitudinally coupled surface acoustic wave resonator filter.

12 more elements

A double mode filter comprising

a substrate;
first, second and third interdigital transducers disposed on a surface of said substrate;
said second and third interdigital transducers being located on opposite sides of said first interdigital transducer in a direction of propagation of surface waves excited and received by said first interdigital transducer;
first and second reflectors located on said substrate at opposite ends of an area in which said first, second and third interdigital transducers are provided;
each of said first, second and third interdigital transducers including a pair of comb electrodes each having at least one electrode finger;
and
a distance L.sub.1 between centers of the at least one electrode finger of said first interdigital transducer and the at least one electrode finger of said second interdigital transducer located adjacent to each other and a distance L.sub.2 between centers of the at least one electrode finger of said first interdigital transducer and the at least one electrode finger of said third interdigital transducer located adjacent to each other being set to different values;
wherein
each of said first and second reflectors has a plurality of electrode fingers arranged substantially perpendicularly to the surface wave propagation direction, a wavelength of surface waves determined by an electrode pitch of the reflectors is .lambda. and said distance L.sub.1 satisfies a relationship (1):
0+n.lambda..ltoreq.L.sub.1 .ltoreq..lambda./2+n.lambda. (1)
(for all values of n where n is any integer)
said distance L.sub.2 satisfies a relationship (2):
.lambda./2+m.lambda..ltoreq.L.sub.2 .ltoreq.(m+1).lambda. (2)
(for all values of m where m is any integer)
said distances L.sub.1 and L.sub.2 do not satisfy a relationship (3):
L.sub.1 =L.sub.2 -.lambda./2+k.lambda. (3)
(for all values of k where k is any integer)
such that two resonant modes are defined in the double mode filter.

15 more elements

A double mode filter comprising:

a substrate;
a plurality of longitudinally coupled surface acoustic wave resonator filters located on said substrate and connected in series to each other, each of said plurality of longitudinally coupled surface acoustic wave filters including:
first, second and third interdigital transducers disposed on a surface of said substrate;
said second and third interdigital transducers being located on opposite sides of said first interdigital transducer in a direction of propagation of surface waves excited and received by said first interdigital transducer;
first and second reflectors located on said substrate at opposite ends of an area in which said first, second and third interdigital transducers are provided;
each of said first, second and third interdigital transducers including a pair of comb electrodes each having at least one electrode finger;
and
a distance L.sub.1 between centers of the at least one electrode finger of said first interdigital transducer and the at least one electrode finger of said second interdigital transducer located adjacent to each other and a distance L.sub.2 between centers of the at least one electrode finger of said first interdigital transducer and the at least one electrode finger of said third interdigital transducer located adjacent to each other being set to different values;
wherein
each of said first and second reflectors has a plurality of electrode fingers arranged substantially perpendicularly to the surface wave propagation direction, a wavelength of surface waves determined by an electrode pitch of the reflectors is .lambda. and said distance L.sub.1 satisfies a relationship (1):
0+n.lambda..ltoreq.L.sub.1 .ltoreq..lambda./2+n.lambda. (1)
(for any value of n where n is an integer)
said distance L.sub.2 satisfies a relationship (2):
.lambda./2+m.lambda..ltoreq.L.sub.2 .ltoreq.(m+1).lambda. (2)
(for any value of m where m is an integer)
said distances L.sub.1 and L.sub.2 do not satisfy a relationship (3):
L.sub.1 =L.sub.2 -.lambda./2+k.lambda. (3)
(for all values of k where k is any integer)
such that two resonant modes are defined in the double mode filter.

16 more elements

Dependencies are inferred from the claim text.