US4028649A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Surface acoustic wave filter
Assignee: Sony Corp
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Filing: 1975-12-19
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Granted: 1977-06-07
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Expires: 1995-12-19
Abstract
Abstract A surface acoustic wave filter having a piezo-electric substrate with a major surface and input and output transducers, each haing a plurality of finger electrodes formed on the major surface to define a propagation path for surface acoustic waves. Finger electrodes of one of the transducers have a step-like configuration to divide the surface wave propagation path into a plurality of surface wave propagation channels. The phase differences of the channels and the length of the steps of the finger electrodes are selected to minimize the multiple reflection echo between the input and output transducers to reduce ripples in the pass band.
Inventors
- 👤 Yasutoshi Komatsu
- 👤 Yuzuru Yanagisawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 18:45
CPC Classifications
H; H03; H03H; H03H9/00; H03H9/46; H03H9/64; H03H9/6489; H03H9/6496; H03H9/02; H03H9/02535; H03H9/02818; H03H9/02842; H03H9/125; H03H9/145; H03H9/14544; H03H9/14547; H03H9/14564
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
192 words
A surface acoustic wave filter comprising: a. a piezo-electric substrate having a major surface; b. input and output transducers formed on the major surface of said substrate, each of said transducer consisting of a plurality of transducer elements; and c. a plurality of surface acoustic wave propagation channels formed on said substrate between said input and output transducer; in which, when the width of a channel k is taken as W k , and the phase difference between the length of the channel k and n times the wave length at the center frequency is taken as θ k (n being a positive integer), the values of θ k and W k are selected to satisfy the following condition: ##EQU5## where R and R' are, respectively, mechanical reflection coefficients of said input and output transducers, Q and Q' are, respectively, electrical reflection coefficients of said input and output transducers, and Σ k W k is normallized as Σ k W k = 1, the transducer elements of said input transducer being located close together and electrically connected, and said plurality of surface acoustic wave propagation channels being formed without an overlapping area.
Claim 2
Dependent Claim
192 words
A surface acoustic wave filter comprising: a. a piezo-electric substrate having a major surface; b. input and output transducers formed on the major surface of said substrate, each of said transducer consisting of a plurality of transducer elements; and c. a plurality of surface acoustic wave propagation channels formed on said substrate between said input and output transducer; in which, when the width of a channel k is taken as W k , and the phase difference between the length of the channel k and n times the wave length at the center frequency is taken as θ k (n being a positive integer), the values of θ k and W k are selected to satisfy the following condition: ##EQU5## where R and R' are, respectively, mechanical reflection coefficients of said input and output transducers, Q and Q' are, respectively, electrical reflection coefficients of said input and output transducers, and Σ k W k is normallized as Σ k W k = 1, the transducer elements of said input transducer being located close together and electrically connected, and said plurality of surface acoustic wave propagation channels being formed without an overlapping area.
Claim 3
Dependent Claim
31 words
A surface acoustic wave filter as claimed in claim 1, in which said input and output transducers are formed integrally and at least one of them has a step type configuration.
Claim 4
Dependent Claim
37 words
A surface acoustic wave filter as claimed in claim 2, in which the channel having the smallest width W k is located in the surface acoustic wave propagation channel in a position removed from the sides thereof.
Claim 5
Dependent Claim
28 words
A surface acoustic wave filter as claimed in claim 1, in which said piezo-electric substrate comprises a lithium niobate single crystal of y cut and Z direction propagation.
Claim 6
Dependent Claim
25 words
A surface acoustic wave filter as claimed in claim 1, in which each of said input and output transducers includes two pairs of transducer elements.
Claim 7
Dependent Claim
49 words
A surface acoustic wave filter as claimed in claim 5, in which said transducer elements are made such that said phase difference satisfies θ ≈ 45° and the widths W 1 and W 2 of said two channels satisfy W 1 : W 2 ≈ 0.85 : 0.15, respectively.
References Cited (Backward Citations)
US3727718A
Cited
US3931597A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-06-06 | 1980-12-06 | 1981-06-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-06-06 | 1984-12-06 | 1985-06-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-06-06 | 1988-12-06 | 1989-06-07 | $7700.00 | Window Closed / Lapsed |