Patent US1489982A successfully refreshed from Google Patents.
US3976944A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Bias optimized FET mixer for varactor tuner
Assignee: RCA Licensing Corp
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Filing: 1975-02-13
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Granted: 1976-08-24
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Expires: 1995-02-13
Abstract
Abstract A field effect transistor may be used as the mixer in a VHF varactor tuner by the use of self-adjusting bias. Both maximum conversion gain can be realized when the oscillator injection voltage is low and low intermodulation and cross modulation products realized at higher oscillator injection voltages. Bias modification is achieved by use of the tuning voltage in a bias control circuit where FET drain current is adjusted while FET bias voltage is maintained substantially constant. Keeping the bias voltage for the FET substantially constant insures constancy of the FET input and output capacitance which in turn preserves the tuner's tuned circuits from being detuned and variably loaded.
Inventors
- 👤 Jack K. Kreng
- 👤 Sanjar Ghaem-maghami
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 15:44
CPC Classifications
H; H03; H03D; H03D7/00; H03D7/12; H03D7/125
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
113 words
In a tuner of the type for receiving an RF signal and having oscillator means including a tuning element responsive to a tuning voltage to generate a channel related signal, wherein the amplitude of said channel related signal differs for the channels within the frequency band being tuned, a FET mixer comprising: a FET having electrode means including at least gate and source electrodes and coupled by said electrode means to receive said RF signal and said channel related signal to generate an IF signal, first means coupled to said electrode means to develop the bias therefore to establish the optimum DC operating point for said FET for one of said channels and,
Claim 2
Dependent Claim
113 words
In a tuner of the type for receiving an RF signal and having oscillator means including a tuning element responsive to a tuning voltage to generate a channel related signal, wherein the amplitude of said channel related signal differs for the channels within the frequency band being tuned, a FET mixer comprising: a FET having electrode means including at least gate and source electrodes and coupled by said electrode means to receive said RF signal and said channel related signal to generate an IF signal, first means coupled to said electrode means to develop the bias therefore to establish the optimum DC operating point for said FET for one of said channels and,
Claim 3
Dependent Claim
38 words
second means coupled to said electrode means and responsive to said tuning voltage to modify FET drain current to establish the optimum DC operating point for said FET for at least another of said channels within said band.
Claim 4
Dependent Claim
38 words
second means coupled to said electrode means and responsive to said tuning voltage to modify FET drain current to establish the optimum DC operating point for said FET for at least another of said channels within said band.
Claim 5
Dependent Claim
31 words
The invention recited in claim 1 wherein said first means controls the bias voltage and drain current of said FET to establish the optimum conversion gain for one of said channels.
Claim 6
Dependent Claim
28 words
The invention recited in claim 1 wherein said second means modifies said drain current to minimize intermodulation and cross modulation products for at least another of said channels.
Claim 7
Dependent Claim
56 words
The invention recited in claim 1 wherein said FET includes at least a gate electrode, a source electrode and a drain electrode, and said first means is coupled to said gate electrode and said source electrode to establish said bias voltage at an essentially constant value during modification of said drain current by said second means.
Claim 8
Dependent Claim
73 words
The invention recited in claim 1 wherein said first means is a resistor network connected to said gate electrode and to said source electrode and said second means is a transistor responsive to said tuning voltage and connected to said resistor biasing network to modify the effective resistance of that portion of said resistor biasing network connected to said source electrode to control the FET drain current in accordance with said tuning voltage.
Claim 9
Dependent Claim
161 words
In a tuner of the type for receiving an RF signal and having oscillator means including a tuning element responsive to a tuning voltage to generate a channel related signal for each of the channels within the band of frequencies being tuned, wherein the amplitude of said channel related signal varies in proportion to said tuning voltage, a FET mixer comprising: a FET having at least gate and source electrode means and coupled by one of said electrode means to receive said RF signal and by one of said electrode means to receive said channel related signals to generate an IF signal, first means coupled to said electrode means to establish a DC operating point for said FET, and second means coupled to one of said electrode means and responsive to said tuning voltage to modify FET drain current to establish the optimum DC operating point for said FET for each channel in accordance with the level of said tuning voltage.
Claim 10
Dependent Claim
161 words
In a tuner of the type for receiving an RF signal and having oscillator means including a tuning element responsive to a tuning voltage to generate a channel related signal for each of the channels within the band of frequencies being tuned, wherein the amplitude of said channel related signal varies in proportion to said tuning voltage, a FET mixer comprising: a FET having at least gate and source electrode means and coupled by one of said electrode means to receive said RF signal and by one of said electrode means to receive said channel related signals to generate an IF signal, first means coupled to said electrode means to establish a DC operating point for said FET, and second means coupled to one of said electrode means and responsive to said tuning voltage to modify FET drain current to establish the optimum DC operating point for said FET for each channel in accordance with the level of said tuning voltage.
References Cited (Backward Citations)
US3493869A
Cited
US3348154A
Cited
US3581211A
Cited
US3626302A
Cited
US3694756A
Cited
US3863136A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-08-24 | 1980-02-23 | 1980-08-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-08-24 | 1984-02-23 | 1984-08-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-08-24 | 1988-02-23 | 1988-08-24 | $7700.00 | Window Closed / Lapsed |