US3825858A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Local oscillator for use in a vhf tuner for a television receiver
Assignee: Hitachi Ltd
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Filing: 1973-02-23
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Granted: 1974-07-23
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Expires: 1993-02-23
Abstract
Abstract A local oscillator for a VHF tuner employing variable capacitance diodes in which a high band tuning coil is tapped at a suitable point and an AFC circuit is connected to this point so as to eliminate variations of the AFC sensitivity depending on the high and low bands. Further, a variable capacitance diode is connected in series with the AFC circuit and tuning voltage is applied to this variable capacitance diode so as to eliminate variations of the AFC sensitivity depending on the channel.
Inventors
- 👤 K Amemiya
- 👤 F Kanai
- 👤 M Kondou
- 👤 K Yamazaki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 19:55
CPC Classifications
H; H03; H03J; H03J7/00; H03J7/02; H03J7/04; H03J7/08; H03J7/10
Claims Analysis
Total Claims: 3
Claim 1
Independent Claim
266 words
A local oscillator for use in a VHF tuner for a television receiver, said oscillator comprising an oscillation circuit including a transistor for generating oScillation, a parallel connection of a first variable capacitance diode and a capacitor, one junction point of said parallel connection being connected to the base of said transistor, and a series connection of a high band tuning coil and a low band tuning coil connected between the other junction point of said parallel connection and ground potential, said high band tuning coil being divided into two coil sections to thereby generate a signal having a frequency determined substantially by the capacitance of said first variable capacitance diode and the inductance of said tuning coils, means connected to said first variable capacitance diode for applying a first control voltage to said diode to thereby change the oscillation frequency of said oscillation circuit, a switching diode for band selection connected to the junction point between said high band tuning coil and said low band tuning coil, means connected to said switching diode for applying a second control voltage to said switching diode, an automatic frequency control circuit connected to the junction point between said two sections of said high band tuning coil, said automatic frequency control circuit including a second variable capacitance diode connected between the junction point of said coil sections and ground potential, and means connected to said second variable capacitance diode for applying a third control voltage to said second variable capacitance diode to thereby adjust the control sensitivity of said automatic frequency control circuit according to the third control voltage.
Claim 2
Dependent Claim
266 words
A local oscillator for use in a VHF tuner for a television receiver, said oscillator comprising an oscillation circuit including a transistor for generating oScillation, a parallel connection of a first variable capacitance diode and a capacitor, one junction point of said parallel connection being connected to the base of said transistor, and a series connection of a high band tuning coil and a low band tuning coil connected between the other junction point of said parallel connection and ground potential, said high band tuning coil being divided into two coil sections to thereby generate a signal having a frequency determined substantially by the capacitance of said first variable capacitance diode and the inductance of said tuning coils, means connected to said first variable capacitance diode for applying a first control voltage to said diode to thereby change the oscillation frequency of said oscillation circuit, a switching diode for band selection connected to the junction point between said high band tuning coil and said low band tuning coil, means connected to said switching diode for applying a second control voltage to said switching diode, an automatic frequency control circuit connected to the junction point between said two sections of said high band tuning coil, said automatic frequency control circuit including a second variable capacitance diode connected between the junction point of said coil sections and ground potential, and means connected to said second variable capacitance diode for applying a third control voltage to said second variable capacitance diode to thereby adjust the control sensitivity of said automatic frequency control circuit according to the third control voltage.
Claim 3
Dependent Claim
79 words
A local oscillator according to claim 1, wherein said automatic frequency control circuit further includes a parallel connection of a third variable capacitance diode and a capacitor, said parallel connection being connected in series with said second variable capacitance diode, and means connected to said third variable capacitance diode for applying the first control voltage to said third variable capacitance diode to thereby adjust the control sensitivity of said automatic frequency control circuit according to the first control voltage.
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) | 1977-07-22 | 1978-01-21 | 1978-07-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-07-22 | 1982-01-21 | 1982-07-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-07-22 | 1986-01-21 | 1986-07-23 | $7700.00 | Window Closed / Lapsed |