US3846723A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Surface wave narrow bandpass filter
Assignee: United States Department of the Navy
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Filing: 1973-06-22
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Granted: 1974-11-05
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Expires: 1993-06-22
Abstract
Abstract A narrow bandpass filter comprising a surface wave device having a transmission characteristic wherein at a selectable center frequency the transmission goes through a very sharp null. The filter is connected in the negative feedback loop of an amplifier circuit. An input signal at the center frequency will not feed back any signal to the input of the amplifier because of the transmission characteristic. As the frequency moves slightly away from the center frequency, the device will begin to transmit.
Inventors
- 👤 P Writer
- 👤 M Schiff
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 09:33
CPC Classifications
H; H03; H03H; H03H9/00; H03H9/46; H03H9/64; H03H9/6406; H03H9/6409
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
164 words
Bandpass filter apparatus comprising: an acoustic-wave propagating medium; a first pair of electrically conductive, U-shaped members deposited on said medium in a symmetrical, interleaved manner with respect to each other and being responsive to incoming signals to launch acoustic waves in said medium at frequencies on either side of a center frequency fo, and to launch no acoustic waves at said frequency fo; second and third pairs of U-shaped members deposited on said medium and spaced apart from said first pair and disposed thereon in an in-line and parallel manner with respect to said first pair, said second and third pairs being electrically connected to each other in a polarity-reversed sense and further being spaced from each other an integral number of wavelengths, N lambda o, where N is equal to any integer and lambda o Vo/fo; and, terminal means connected to the output of said third pair for providing an output signal having a bandwidth proportional said number of wavelengths, N lambda o.
Claim 2
Dependent Claim
164 words
Bandpass filter apparatus comprising: an acoustic-wave propagating medium; a first pair of electrically conductive, U-shaped members deposited on said medium in a symmetrical, interleaved manner with respect to each other and being responsive to incoming signals to launch acoustic waves in said medium at frequencies on either side of a center frequency fo, and to launch no acoustic waves at said frequency fo; second and third pairs of U-shaped members deposited on said medium and spaced apart from said first pair and disposed thereon in an in-line and parallel manner with respect to said first pair, said second and third pairs being electrically connected to each other in a polarity-reversed sense and further being spaced from each other an integral number of wavelengths, N lambda o, where N is equal to any integer and lambda o Vo/fo; and, terminal means connected to the output of said third pair for providing an output signal having a bandwidth proportional said number of wavelengths, N lambda o.
Claim 3
Dependent Claim
18 words
The apparatus of claim 1 wherein said propagating medium comprises quartz and wherein said members comprise aluminum devices.
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) | 1977-11-04 | 1978-05-06 | 1978-11-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-11-04 | 1982-05-06 | 1982-11-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-11-04 | 1986-05-06 | 1986-11-05 | $7700.00 | Window Closed / Lapsed |