Patent US2990311A successfully refreshed from Google Patents.
US3568082A
Expired / Lapsed
US
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Active crystal filter with a transfer function of a wanted degree
Assignee: Telefonaktiebolaget LM Ericsson AB
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Filing: 1968-09-03
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Granted: 1971-03-02
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Expires: 1988-09-03
Abstract
Abstract An active band pass filter includes a plurality of serially connected crystals which connect the input of the filter to an emitter-follower amplifier. A first plurality of resistors connected at alternate junctions of the crystals to the output of the amplifier and a second plurality of resistors connect the remaining junctions of the crystals to a signal level means which has a level different from the output of the amplifier.
Inventors
- 👤 Tore Torstensson Fjallbrant
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 10:49
CPC Classifications
H; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H9/00; H03H9/46; H03H9/54; H03H9/545
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
225 words
An active band-pass filter having an n-degree transfer function comprising n crystals, connected in series, each of said n crystals operating as a series resonant circuit with the same resonant frequency, signal input means connected to one end of said serially connected crystals, a signal amplifier having a common terminal, an input terminal and an output terminal, means for applying an operating voltage to said common terminal, means for connecting the input terminal of said signal amplifIer to the other end of said serially connected crystals, an output resistor connecting the output terminal of said signal amplifier to ground, a plurality of first resistors, each of said first resistors having one terminal connected to a different one of alternate junctions of said serially connected crystals starting with such junction nearest said other end of said serially connected crystals, respectively, the other terminal of each of said first resistors being connected to said output terminal of said signal amplifier, a plurality of second resistors, each of said second resistors having one terminal connected to a different one of the remaining junctions of said serially connected crystals and said other end of said serially connected crystals, respectively, and means for maintaining the other terminals of said second resistors at at least one signal level different from the signal level of the output terminal of said signal amplifier.
Claim 2
Dependent Claim
225 words
An active band-pass filter having an n-degree transfer function comprising n crystals, connected in series, each of said n crystals operating as a series resonant circuit with the same resonant frequency, signal input means connected to one end of said serially connected crystals, a signal amplifier having a common terminal, an input terminal and an output terminal, means for applying an operating voltage to said common terminal, means for connecting the input terminal of said signal amplifIer to the other end of said serially connected crystals, an output resistor connecting the output terminal of said signal amplifier to ground, a plurality of first resistors, each of said first resistors having one terminal connected to a different one of alternate junctions of said serially connected crystals starting with such junction nearest said other end of said serially connected crystals, respectively, the other terminal of each of said first resistors being connected to said output terminal of said signal amplifier, a plurality of second resistors, each of said second resistors having one terminal connected to a different one of the remaining junctions of said serially connected crystals and said other end of said serially connected crystals, respectively, and means for maintaining the other terminals of said second resistors at at least one signal level different from the signal level of the output terminal of said signal amplifier.
Claim 3
Dependent Claim
25 words
The active band-pass filter of claim 1 wherein the other terminal of each of said second resistors is maintained at the same constant DC voltage.
Claim 4
Dependent Claim
19 words
The active band-pass filter of claim 2 wherein the other terminal of each of said second resistors is grounded.
Claim 5
Dependent Claim
60 words
The active band-pass filter of claim 2 and further comprising a third plurality of resistors, means for connecting one terminal of each of said third resistors to a different one of each of said one terminals of said second resistors, respectively and means for maintaining the other terminal of each of said third resistors at the same constant DC voltage.
Claim 6
Dependent Claim
56 words
The active band-pass filter of claim 3 and further comprising a third plurality of resistors, means for connecting one terminal of each of said third resistors to a different one of each of said one terminal of said second resistors, respectively, and means for connecting the other terminal of each of said third resistors to ground.
Claim 7
Dependent Claim
45 words
The active band-pass filter of claim 1 wherein said output resistor includes a plurality of different tapping points between the terminals thereof, and further comprising means for connecting said other terminal of each of said second resistors to a different one of said tapping points.
Claim 8
Dependent Claim
100 words
The active band-pass filter of claim 1 and further comprising a second signal amplifier having an input terminal and first and second output terminals, a two-terminal source of operating potential, a first tapped resistor connecting the first output terminal of said second signal amplifier to one terminal of said source of operating potential, a second tapped resistor connecting the second output terminal of said second signal amplifier to the other terminal of said source of operating potential, and means for connecting the other terminal of each of said second resistors to different taps of said first and second tapped resistors.
References Cited (Backward Citations)
US3064213A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-03-01 | 1974-08-31 | 1975-03-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-03-01 | 1978-08-31 | 1979-03-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-03-01 | 1982-08-31 | 1983-03-02 | $7700.00 | Window Closed / Lapsed |