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US4649357A
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Surface-acoustic-wave filter
Assignee: Oki Electric Industry Co Ltd
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Filing: 1986-02-25
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Granted: 1987-03-10
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Expires: 2006-02-25
Abstract
Abstract A surface-acoustic-wave filter is of a multi-transducer arrangement including a plurality of input interdigital transducers and a plurality of output interdigital transducers. These input and output transducers are alternately and parallelly disposed on a piezo-electric substrate so as to be spaced intercentral distances l 1 through l n apart. When one of the intercentral distances is a reference distance l 1 , the respective intercentral distances l 1 through l n satisfies the following relationships: l.sub.1 =m.sub.1 ·λ, l.sub.2 =l.sub.1+ m.sub.2 ·λ, l 3 =l 1 +m 3 ·λ, . . . l n =l 1 +m n ·λ where m 1 is an arbitrary positive real number, m 2 through m n are respectively arbitrary integers (0, ±1, ±2, . . . ), and λ is a wavelength of the surface-acoustic-wave. The surface-acoustic-wave filter provides a good filter characteristic having sufficient effective attenuation in the attenuation region without deteriorating the filter characteristic in a pass-band thereof.
Inventors
- 👤 Kiyoshi Nagai
- 👤 Nobuyoshi Sakamoto
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 15:23
CPC Classifications
H; H03; H03H; H03H9/00; H03H9/46; H03H9/64; H03H9/6423; H03H9/6426; H03H9/02; H03H9/125; H03H9/145; H03H9/14544; H03H9/1455
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
207 words
A surface-acoustic-wave filter comprising a substrate through which a surface-acoustic-wave propagates, and input transducers and output transducers each composed of a plurality of surface-acoustic-wave interdigital transducers, for converting an electrical signal into a surface acoustic wave and vice versa, formed on said substrate, said input transducers and said output transducers being alternately disposed in the propagation direction of the surface-acoustic-wave; wherein said surface-acoustic-wave interdigital transducers are disposed such that, when an intercentral distance between the centers of two mutually adjoining surface-acoustic-wave interdigital transducers is a reference distance l 1 and when the other intercentral distances between the centers of the mutually adjoining respective surface-acoustic-wave interdigital transducers besides said reference distance l 1 , are l 2 through l n respectively, the following equations are satisfied: ##EQU2## wherein λ is a wavelength of the surface-acoustic-wave and is defined by λ=V/fo when the propagation velocity of the surface-acoustic-wave is V and a center frequency of the surface-acoustic-wave filter is fo, and m 1 is an arbitrary positive real number, and m 2 through m n are respectively arbitrary integers, and said surface-acoustic-wave interdigital transducers are arranged such that at least one distance selected from among said respective distances l 1 through l n differs from the other remaining distances.
Claim 2
Dependent Claim
207 words
A surface-acoustic-wave filter comprising a substrate through which a surface-acoustic-wave propagates, and input transducers and output transducers each composed of a plurality of surface-acoustic-wave interdigital transducers, for converting an electrical signal into a surface acoustic wave and vice versa, formed on said substrate, said input transducers and said output transducers being alternately disposed in the propagation direction of the surface-acoustic-wave; wherein said surface-acoustic-wave interdigital transducers are disposed such that, when an intercentral distance between the centers of two mutually adjoining surface-acoustic-wave interdigital transducers is a reference distance l 1 and when the other intercentral distances between the centers of the mutually adjoining respective surface-acoustic-wave interdigital transducers besides said reference distance l 1 , are l 2 through l n respectively, the following equations are satisfied: ##EQU2## wherein λ is a wavelength of the surface-acoustic-wave and is defined by λ=V/fo when the propagation velocity of the surface-acoustic-wave is V and a center frequency of the surface-acoustic-wave filter is fo, and m 1 is an arbitrary positive real number, and m 2 through m n are respectively arbitrary integers, and said surface-acoustic-wave interdigital transducers are arranged such that at least one distance selected from among said respective distances l 1 through l n differs from the other remaining distances.
Claim 3
Dependent Claim
34 words
A surface-acoustic-wave filter according to claim 1, wherein said respective intercentral distances l 1 through l n between the centers of said mutually adjoining surface-acoustic-wave interdigital transducers differ partly or wholly from each other.
Claim 4
Dependent Claim
24 words
A surface-acoustic-wave filter according to claim 1, wherein said reference distance l 1 is an integral multiple of the wavelength λ of the surface-acoustic-wave.
Claim 5
Dependent Claim
24 words
A surface-acoustic-wave filter according to claim 2, wherein said reference distance l 1 is an integral multiple of the wavelength λ of the surface-acoustic-wave.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-03-09 | 1990-09-08 | 1991-03-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-03-09 | 1994-09-08 | 1995-03-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-03-09 | 1998-09-08 | 1999-03-10 | $7700.00 | Window Closed / Lapsed |