Patent US4005378A successfully refreshed from Google Patents.
US4005378A
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Surface acoustic wave filter
Assignee: United States Department of the Air Force
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Filing: 1975-11-25
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Granted: 1977-01-25
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Expires: 1995-11-25
Abstract
Abstract A surface acoustic wave bandpass filter having a flat frequency response in the passband and an exponentially decaying out-of-band response is realized by designing its transducer electrodes to have an appropriate number of discretely apodized interdigital fingers. The apodization or overlap coefficients H o (N) of adjacent fingers are determined from an analytically derived expression that incorporates factors for the filter time length parameter, the filter center frequency, bandwidth, transition bandwidth falloff, and a ripple reduction parameter.
Inventors
- 👤 Andrew J. Slobodnik, Jr.
- 👤 Kenneth R. Laker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 04:19
CPC Classifications
H; H03; H03H; H03H9/00; H03H9/02; H03H9/125; H03H9/145; H03H9/14517; H03H9/1452; H03H9/46; H03H9/64; H03H9/6489
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
82 words
A surface acoustic wave filter transducer having 4(f o τ)+2 interdigital fingers and finger overlap coefficients H o [N] determined by the equation ##EQU8##wherein N is the number of gaps between interdigital fingers τ is the filter time length parameter, f o is the filter center frequency, B is the filter bandwidth, K is the transistor bandwidth fall off parameter, I o is a modified Bessel function of the first kind and zero order and W a is the ripple reduction parameter.
Claim 2
Dependent Claim
82 words
A surface acoustic wave filter transducer having 4(f o τ)+2 interdigital fingers and finger overlap coefficients H o [N] determined by the equation ##EQU8##wherein N is the number of gaps between interdigital fingers τ is the filter time length parameter, f o is the filter center frequency, B is the filter bandwidth, K is the transistor bandwidth fall off parameter, I o is a modified Bessel function of the first kind and zero order and W a is the ripple reduction parameter.
Claim 3
Independent Claim
122 words
The method of constructing a surface acoustic wave filter comprising the steps of selecting filter parameters for a filter time length parameter τ, a filter center frequency f o , a filter bandwidth B, a transition bandwidth fall off parameter k and a ripple reduction parameter W a , the values of τ and f o being such that the expression 2(f o τ) is an integer, providing a surface acoustic wave substrate member having properties consistent with said selected filter parameters, and affixing to the acoustic wave propagating surface of said substrate member an interdigital transducer having 4(f o τ)+2 interdigital fingers with N gap therebetween, the overlap coefficient H o (N) of adjacent fingers being defined by the expression ##EQU9##
Claim 4
Independent Claim
122 words
The method of constructing a surface acoustic wave filter comprising the steps of selecting filter parameters for a filter time length parameter τ, a filter center frequency f o , a filter bandwidth B, a transition bandwidth fall off parameter k and a ripple reduction parameter W a , the values of τ and f o being such that the expression 2(f o τ) is an integer, providing a surface acoustic wave substrate member having properties consistent with said selected filter parameters, and affixing to the acoustic wave propagating surface of said substrate member an interdigital transducer having 4(f o τ)+2 interdigital fingers with N gap therebetween, the overlap coefficient H o (N) of adjacent fingers being defined by the expression ##EQU9##
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) | 1980-01-25 | 1980-07-26 | 1981-01-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-01-25 | 1984-07-26 | 1985-01-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-01-25 | 1988-07-26 | 1989-01-25 | $7700.00 | Window Closed / Lapsed |