US4835608A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Image trap filter circuit
Assignee: Zenith Electronics LLC
•
Filing: 1988-05-31
•
Granted: 1989-05-30
•
Expires: 2008-05-31
Abstract
Abstract A varactor diode tuner includes a tunable image frequency trap in its input circuit. The trap is part of a tunable bandpass filter and forms a tapped capacitance matching network for UHF television signal carrier frequencies and a low impedance shunt at image frequencies. The trap is formed of discrete capacitors, an inductor and a tunable varactor diode.
Inventors
- 👤 Mark J. Lachiw
- 👤 Peter Strammello
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 15:34
CPC Classifications
H; H03; H03J; H03J3/00; H03J3/02; H03J3/16; H03J3/18; H03J3/185
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
86 words
In a television signal tuner of the type having a varactor diode-tuned bandpass filter input circuit and varactor diode-tuned interstage filter and oscillator circuits for providing a fixed frequency IF output signal in response to television signals of differing carrier frequencies, the improvement comprising: a tunable trap circuit in the bandpass filter for restricting image frequency input signals, said tunable trap circuit functioning as a tapped capacitance matching network for said television signal carrier frequencies and as a low impedance capacitance shunt at said image frequency.
Claim 2
Dependent Claim
86 words
In a television signal tuner of the type having a varactor diode-tuned bandpass filter input circuit and varactor diode-tuned interstage filter and oscillator circuits for providing a fixed frequency IF output signal in response to television signals of differing carrier frequencies, the improvement comprising: a tunable trap circuit in the bandpass filter for restricting image frequency input signals, said tunable trap circuit functioning as a tapped capacitance matching network for said television signal carrier frequencies and as a low impedance capacitance shunt at said image frequency.
Claim 3
Dependent Claim
45 words
The tuner of claim 1 wherein said capacitance shunt comprises an inductor, a varactor diode and a resistor connected in series; a first trim capacitor connected across said resistor and a second trim capacitor connected across the combination of said resistor and said varactor diode.
Claim 4
Dependent Claim
94 words
A television signal tuner comprising: a source of DC tuning voltage; an input circuit for receiving UHF television signals; an inductor; a first varactor diode connected between said input circuit and said inductor and coupled to said source of DC tuning voltage; an amplifier coupled to the junction of said first varactor diode and said inductor; a second varactor diode and a resistor connected in series with said inductor; a first trim capacitor connected across said resistor; and a second trim capacitor connected across the combination of said second varactor diode and said resistor.
Claim 5
Dependent Claim
94 words
A television signal tuner comprising: a source of DC tuning voltage; an input circuit for receiving UHF television signals; an inductor; a first varactor diode connected between said input circuit and said inductor and coupled to said source of DC tuning voltage; an amplifier coupled to the junction of said first varactor diode and said inductor; a second varactor diode and a resistor connected in series with said inductor; a first trim capacitor connected across said resistor; and a second trim capacitor connected across the combination of said second varactor diode and said resistor.
Claim 6
Dependent Claim
48 words
The tuner of claim 3, further including a tunable oscillator; a mixer and a tunable interstage; said tunable interstage being coupled between said amplifier and said mixer; said oscillator supplying signals to said mixer and said source of tuning voltage being coupled to said oscillator and said interstage.
References Cited (Backward Citations)
US3562417A
Cited
US4204166A
Cited
US4361909A
Cited
US4399559A
Cited
US4368541A
Cited
JPS58105614A
Cited
JPS5961284A
Cited
JPS5981927A
Cited
US4760535A
Cited
US4601062A
Cited
US4662001A
Cited
US4771332A
Cited
JPH0680325A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-05-29 | 1992-11-28 | 1993-05-30 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-05-29 | 1996-11-28 | 1997-05-30 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-05-29 | 2000-11-28 | 2001-05-30 | $7700.00 | Window Closed / Lapsed |