US4468642A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Band pass filter device
Assignee: Hitachi Ltd
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Filing: 1982-06-07
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Granted: 1984-08-28
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Expires: 2002-06-07
Abstract
Abstract A band pass filter device has transducers comprised of thin metal stripes or slits formed on a surface of a piezoelectric plate for propagation of acoustic waves. The device comprises first and second band pass filters at least one of which is made unidirectional. The first band pass filter includes a first acousto-electric transducer and electro-acoustic transducers disposed on opposite sides of the first acousto-electric transducer and connected in common to an input signal source, and the second band pass filter includes a second electro-acoustic transducer connected electrically to the first acousto-electric and second acousto-electric transducers disposed on opposite sides of the second electro-acoustic transducer and connected in common to an output terminal, whereby a frequency characteristic can be obtained wherein loss is reduced in a pass band and increased in a stop band, and rising at the boundary between the pass band and stop band is made sharp. The small-sized band pass filter device having the above frequency characteristic is used for communication apparatus at VHF or UHF.
Inventors
- 👤 Mitsutaka Hikita
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 22:30
CPC Classifications
H; H03; H03H; H03H9/00; H03H9/46; H03H9/64; H03H9/6489; H03H9/02; H03H9/02535; H03H9/02637; H03H9/02685; H03H9/02692; H03H9/027
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
211 words
A band pass filter device comprising: a first band pass filter including a first acousto-electric transducer and first electro-acoustic transducers disposed on opposite sides of the first acousto-electric transducer and adapted for connection in common to an input signal source, said first acousto-electric transducer having pairs of fingers; a second band pass filter including a second electro-acoustic transducer connected electrically to said first acousto-electric transducer and second acousto-electric transducers disposed on opposite sides of the second electro-acoustic transducer and connected in common to an output terminal, said second electro-acoustic transducer having pairs of fingers, and said first acousto-electric transducer having the same structure as that of said second electro-acoustic transducer in which the number N of pairs of fingers in each of said first acousto-electric transducer and said second electro-acoustic transducer substantially is equal to 1.5/k 2 , where k 2 represents the electromechanical coupling constant of a piezoelectric plate on which said fingers are formed and is expressed by k 2 =2(v f -v m )v f , v f representing the velocity of a surface acoustic wave propagating along a free surface of said plate and v m representing the velocity of a surface acoustic wave propagating along a thin metal coated portion of the surface of said plate.
Claim 2
Dependent Claim
211 words
A band pass filter device comprising: a first band pass filter including a first acousto-electric transducer and first electro-acoustic transducers disposed on opposite sides of the first acousto-electric transducer and adapted for connection in common to an input signal source, said first acousto-electric transducer having pairs of fingers; a second band pass filter including a second electro-acoustic transducer connected electrically to said first acousto-electric transducer and second acousto-electric transducers disposed on opposite sides of the second electro-acoustic transducer and connected in common to an output terminal, said second electro-acoustic transducer having pairs of fingers, and said first acousto-electric transducer having the same structure as that of said second electro-acoustic transducer in which the number N of pairs of fingers in each of said first acousto-electric transducer and said second electro-acoustic transducer substantially is equal to 1.5/k 2 , where k 2 represents the electromechanical coupling constant of a piezoelectric plate on which said fingers are formed and is expressed by k 2 =2(v f -v m )v f , v f representing the velocity of a surface acoustic wave propagating along a free surface of said plate and v m representing the velocity of a surface acoustic wave propagating along a thin metal coated portion of the surface of said plate.
Claim 3
Dependent Claim
136 words
A band pass filter device according to claim 1, wherein each of said first and second electro-acoustic transducers and said first and second acousto-electric transducers is constituted by a plurality of transducer elements, the transducer elements of said first electro-acoustic transducers and those of said first acousto-electric transducer being alternately disposed in a direction parallel with the propagating direction of a surface acoustic wave along the surface of said plate, the transducer elements of said second electro-acoustic transducer and those of said second acousto-electric transducers being alternately disposed in a direction parallel with the propagating direction of a surface acoustic wave along the surface of said plate, and each of said transducer elements of said first acousto-electric transducer being in image impedance connection with the corresponding one of said transducer elements of said second electro-acoustic transducer.
Claim 4
Dependent Claim
26 words
A band pass filter device according to claim 2, wherein the outermost ones of said transducer elements of said first electro-acoustic transducers are unidirectional transducer elements.
Claim 5
Dependent Claim
26 words
A band pass filter device according to claim 2, wherein the outermost ones of said transducer elements of said second acousto-electric transducers are unidirectional transducer elements.
Claim 6
Dependent Claim
31 words
A band pass filter device according to claim 2, wherein the outermost ones of said transducer elements of said first electro-acoustic transducers and said second acousto-electric transducers are unidirectional transducer elements.
Claim 7
Dependent Claim
17 words
A band pass filter device according to claim 1, wherein said first electro-acoustic transducers are unidirectional transducers.
Claim 8
Dependent Claim
17 words
A band pass filter device according to claim 1, wherein said second acousto-electric transducers are unidirectional transducers.
Claim 9
Dependent Claim
22 words
A band pass filter device according to claim 1, wherein said first electro-acoustic transducers and said second acousto-electric transducers are unidirectional transducers.
Claim 10
Dependent Claim
28 words
A band pass filter device according to claim 6, 7 or 8, wherein each of said unidirectional transducers is constituted by a bidirectional transducer and a multi-strip coupler.
Claim 11
Dependent Claim
30 words
A band pass filter device according to claim 3, 4 or 5, wherein each of said unidirectional transducer elements is constituted by a bidirectional transducer element and a multi-strip coupler.
Claim 12
Dependent Claim
27 words
A band pass filter device according to claim 6, 7 or 8, wherein each of said unidirectional transducers is constituted by a bidirectional transducer and a reflector.
Claim 13
Dependent Claim
29 words
A band pass filter device according to claim 3, 4 or 5, wherein each of said unidirectional transducer elements is constituted by a bidirectional transducer element and a reflector.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-08-28 | 1988-02-27 | 1988-08-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-08-28 | 1992-02-27 | 1992-08-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-08-28 | 1996-02-27 | 1996-08-28 | $7700.00 | Window Closed / Lapsed |