US3723773A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Multiple resonator active filter
Assignee: SRI International Inc
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Filing: 1971-05-27
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Granted: 1973-03-27
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Expires: 1991-05-27
Abstract
Abstract An active inductance of essentially infinite Q for use at microwave frequencies is used as a general circuit element, particularly in single and multiple resonator filters and in channel separators for multiplexing applications. The basic circuit element is configured (constructed) utilizing the emitter electrode of a transistor as the input port, the collector electrode is grounded, and the base electrode circuit is adjusted so inductance and useful negative resistance are translated to the emitter from the base circuit at substantially the center of the desired frequency band of operation. The transistor current is adjusted so that the internal emitter resistance of the transistor essentially cancels the negative translated resistance to yield a synthesized microwave inductance with very high Q.
Inventors
- 👤 D Adams
- 👤 R Ho
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 22:29
CPC Classifications
H; H04; H04J; H04J1/00; H04J1/02; H04J1/08; H04J1/085; H03; H03H; H03H11/00; H03H11/02; H03H11/04; H03H11/12; H03H11/1213; H03H11/46; H03H11/48
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
265 words
A multiple resonator filter for operation at microwave frequencies having a filter input terminal, a filter output terminal, and a filter reference potential terminaL, said filter including in combination a plurality of active filter elements and coupling circuit means connecting said active filter elements to each other and to said filter input and output terminals, each of said active filter elements intended for operation at a predetermined frequency greater than 100 MHz and including an input terminal, a reference potential terminal, and a DC biased transistor having emitter, collector and base electrodes and inherent base-collector capacitance, inherent base resistance, and inherent emitter resistance, said emitter electrode connected to said input terminal and said inherent emitter resistance having a predetermined value re given approximately by re 26/I ohms where I is the DC emitter current in milliamps, base circuit means connecting said base electrode to said reference potential terminal, collector circuit means connecting said collector electrode to said reference potential terminal whereby said inherent base collector capacitance appears in parallel with said base circuit means, said base circuit means comprising an inductance in series with said inherent base resistance, said inductance having an inductance value such that as translated as a frequency dependent negative resistance at said emitter electrode, the negative resistance is approximately equal to -re at said predetermined frequency whereby the total resistance at the emitter electrode is approximately zero at said predetermined frequency, said coupling circuit means including a series connected capacitor between said active filter elements whereby the effective predetermined frequency of operation of each active filter element is offset in frequency.
Claim 2
Dependent Claim
265 words
A multiple resonator filter for operation at microwave frequencies having a filter input terminal, a filter output terminal, and a filter reference potential terminaL, said filter including in combination a plurality of active filter elements and coupling circuit means connecting said active filter elements to each other and to said filter input and output terminals, each of said active filter elements intended for operation at a predetermined frequency greater than 100 MHz and including an input terminal, a reference potential terminal, and a DC biased transistor having emitter, collector and base electrodes and inherent base-collector capacitance, inherent base resistance, and inherent emitter resistance, said emitter electrode connected to said input terminal and said inherent emitter resistance having a predetermined value re given approximately by re 26/I ohms where I is the DC emitter current in milliamps, base circuit means connecting said base electrode to said reference potential terminal, collector circuit means connecting said collector electrode to said reference potential terminal whereby said inherent base collector capacitance appears in parallel with said base circuit means, said base circuit means comprising an inductance in series with said inherent base resistance, said inductance having an inductance value such that as translated as a frequency dependent negative resistance at said emitter electrode, the negative resistance is approximately equal to -re at said predetermined frequency whereby the total resistance at the emitter electrode is approximately zero at said predetermined frequency, said coupling circuit means including a series connected capacitor between said active filter elements whereby the effective predetermined frequency of operation of each active filter element is offset in frequency.
Claim 3
Dependent Claim
302 words
A multiple resonator filter for operation at microwave frequencies having a filter input terminal, a filter output terminal, and a filter reference potential terminal, said filter including in combination a plurality of active filter elements and coupling circuit means connecting said active filter elements to each other and to said filter input and output terminals, each of said active filter elements intended for operation at a predetermined frequency greater than 100 MHz and including an input terminal, a reference potential terminal, and a DC biased transistor having emitter, collector and base electrodes and inherent base-collector capacitance, inherent base resistance, and inherent emitter resistance, said emitter electrode connected to said input terminal and said inherent emitter resistance having a predetermined value re given approximately by re 26/I ohms where I is the DC emitter current in milliamps, base circuit means connecting said base electrode to said reference potential terminal, collector circuit means connecting said collector electrode to said reference potential terminal whereby said inherent base collector capacitance appears in parallel with said base circuit means, said base circuit means comprising an inductance in series with said inherent base resistance, said inductance having an inductance value such that as translated as a frequency dependent negative resistance at said emitter electrode, the negative resistance is approximately equal to -re at said predetermined frequency whereby the total resistance at the emitter electrode is approximately zero at said predetermined frequency, said coupling circuit means including a plurality of coupling capacitors and a plurality of shunt resonance tuning capacitors, said coupling capacitors connected in series between said filter input and output terminals, said input terminals of each individual filter element each connected between a pair of said coupling capacitors, said shunt tuning capacitors each connected between the said input and reference potential terminals of an individual filter element.
Claim 4
Dependent Claim
302 words
A multiple resonator filter for operation at microwave frequencies having a filter input terminal, a filter output terminal, and a filter reference potential terminal, said filter including in combination a plurality of active filter elements and coupling circuit means connecting said active filter elements to each other and to said filter input and output terminals, each of said active filter elements intended for operation at a predetermined frequency greater than 100 MHz and including an input terminal, a reference potential terminal, and a DC biased transistor having emitter, collector and base electrodes and inherent base-collector capacitance, inherent base resistance, and inherent emitter resistance, said emitter electrode connected to said input terminal and said inherent emitter resistance having a predetermined value re given approximately by re 26/I ohms where I is the DC emitter current in milliamps, base circuit means connecting said base electrode to said reference potential terminal, collector circuit means connecting said collector electrode to said reference potential terminal whereby said inherent base collector capacitance appears in parallel with said base circuit means, said base circuit means comprising an inductance in series with said inherent base resistance, said inductance having an inductance value such that as translated as a frequency dependent negative resistance at said emitter electrode, the negative resistance is approximately equal to -re at said predetermined frequency whereby the total resistance at the emitter electrode is approximately zero at said predetermined frequency, said coupling circuit means including a plurality of coupling capacitors and a plurality of shunt resonance tuning capacitors, said coupling capacitors connected in series between said filter input and output terminals, said input terminals of each individual filter element each connected between a pair of said coupling capacitors, said shunt tuning capacitors each connected between the said input and reference potential terminals of an individual filter element.
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) | 1976-03-26 | 1976-09-25 | 1977-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-03-26 | 1980-09-25 | 1981-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-03-26 | 1984-09-25 | 1985-03-27 | $7700.00 | Window Closed / Lapsed |