US4245350A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic gain control system for direct-access television receiver
Assignee: Zenith Electronics LLC
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Filing: 1979-06-22
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Granted: 1981-01-13
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Expires: 1999-06-22
Abstract
Abstract A control system is described for use in a television receiver adapted to receive multi-band television signals and which has a direct-access type tuning system. In such a tuning system, the receiver employs at least one local oscillator, the output of which is applied to a prescaler for dividing down the frequency of the oscillator signal. Frequently, the oscillator signal fluctuates in amplitude as the oscillator is tuned from channel to channel and from one frequency band to another frequency band. To compensate for such amplitude fluctuations, the control system confines the amplitude of the oscillator signal to an amplitude range which the prescaler can reliably handle and applies the amplitude-controlled oscillator signal to the prescaler.
Inventors
- 👤 Frederic J. Moore
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 10:53
CPC Classifications
H; H03; H03L; H03L7/00; H03L7/06; H03L7/16; H03L7/18; H03L7/183; H03G; H03G3/00; H03G3/20; H03G3/30; H03G3/3036
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
277 words
In a television receiver adapted to receive multi-band television signals and having a direct access tuning system including at least one local oscillator which is tuneable over a plurality of the receivable television bands, and having a prescaler for counting and dividing-down the signal generated by the local oscillator to develop a lower frequency oscillator signal for further processing by the tuning system, a control system for automatically compensating for amplitude variations in the oscillator signal as the oscillator is tuned from channel to channel and from band to band so as to confine the amplitude of the oscillator signal to a predetermined amplitude range within which the prescaler is adapted to count, comprising: gain-control means receiving a control signal and the oscillator signal for controlling the amplitude of the oscillator signal as a function of the value of the control signal; means receiving the gain-controlled oscillator signal from said gain-control means for detecting the amplitude thereof and for generating the control signal whose value is representative of the difference between the detected amplitude of the gain-controlled oscillator signal and the prescaler's amplitude range; means for applying the control signal to said gain-control means to adjust its gain such that the gain-controlled oscillator signal has an amplitude within the predetermined amplitude range of the prescaler irrespective of the frequency to which the oscillator is tuned; and means for applying the gain-controlled oscillator signal to the prescaler, whereby an oscillator signal whose amplitude fluctuates as the oscillator is tuned from channel to channel and from band to band is automatically brought within the amplitude range of the prescaler and is thereby reliably counted and divided-down by the prescaler.
Claim 2
Dependent Claim
277 words
In a television receiver adapted to receive multi-band television signals and having a direct access tuning system including at least one local oscillator which is tuneable over a plurality of the receivable television bands, and having a prescaler for counting and dividing-down the signal generated by the local oscillator to develop a lower frequency oscillator signal for further processing by the tuning system, a control system for automatically compensating for amplitude variations in the oscillator signal as the oscillator is tuned from channel to channel and from band to band so as to confine the amplitude of the oscillator signal to a predetermined amplitude range within which the prescaler is adapted to count, comprising: gain-control means receiving a control signal and the oscillator signal for controlling the amplitude of the oscillator signal as a function of the value of the control signal; means receiving the gain-controlled oscillator signal from said gain-control means for detecting the amplitude thereof and for generating the control signal whose value is representative of the difference between the detected amplitude of the gain-controlled oscillator signal and the prescaler's amplitude range; means for applying the control signal to said gain-control means to adjust its gain such that the gain-controlled oscillator signal has an amplitude within the predetermined amplitude range of the prescaler irrespective of the frequency to which the oscillator is tuned; and means for applying the gain-controlled oscillator signal to the prescaler, whereby an oscillator signal whose amplitude fluctuates as the oscillator is tuned from channel to channel and from band to band is automatically brought within the amplitude range of the prescaler and is thereby reliably counted and divided-down by the prescaler.
Claim 3
Dependent Claim
243 words
In a television receiver having a direct-access tuning system including a VHF local oscillator, a UHF local oscillator, a prescaler for counting and dividing-down the signals generated by the local oscillators to develop lower frequency oscillator signals for further processing by the tuning system, a control system for automatically adjusting the amplitude of the signals from the oscillators to a predetermined amplitude range within which the prescaler is adapted to count, comprising: means for combining the outputs of the VHF and UHF oscillators to generate a single RF signal; gain-control means receiving a control signal and the RF signal for controlling the amplitude of the RF signal as a function of the value of the control signal; means for detecting the amplitude of the RF signal output of said gain-control means and for generating the control signal whose value is representative of the difference between the detected amplitude of the RF signal output and the prescaler's amplitude range; means for applying the control signal to said gain-control means to adjust its gain such that its RF signal output has an amplitude within the predetermined amplitude range of the prescaler irrespective of the frequency of the RF signal; and means for applying the RF signal output of said gain-control means to the prescaler, whereby oscillator signals having amplitudes which are beyond the amplitude range of the prescaler are automatically adjusted to the latter range and are thereby reliably counted and divided-down by the prescaler.
Claim 4
Dependent Claim
243 words
In a television receiver having a direct-access tuning system including a VHF local oscillator, a UHF local oscillator, a prescaler for counting and dividing-down the signals generated by the local oscillators to develop lower frequency oscillator signals for further processing by the tuning system, a control system for automatically adjusting the amplitude of the signals from the oscillators to a predetermined amplitude range within which the prescaler is adapted to count, comprising: means for combining the outputs of the VHF and UHF oscillators to generate a single RF signal; gain-control means receiving a control signal and the RF signal for controlling the amplitude of the RF signal as a function of the value of the control signal; means for detecting the amplitude of the RF signal output of said gain-control means and for generating the control signal whose value is representative of the difference between the detected amplitude of the RF signal output and the prescaler's amplitude range; means for applying the control signal to said gain-control means to adjust its gain such that its RF signal output has an amplitude within the predetermined amplitude range of the prescaler irrespective of the frequency of the RF signal; and means for applying the RF signal output of said gain-control means to the prescaler, whereby oscillator signals having amplitudes which are beyond the amplitude range of the prescaler are automatically adjusted to the latter range and are thereby reliably counted and divided-down by the prescaler.
Claim 5
Dependent Claim
58 words
A control system as set forth in claim 2 wherein the receiver is adapted to receive television signals in the VHF, CATV and UHF bands, and wherein said gain-control means is adapted to control the amplitude of RF signals which are generated by the oscillators in response to receipt of a television signal in any of said bands.
Claim 6
Dependent Claim
16 words
A control system as set forth in claim 3 wherein said combining means includes a diplexer.
Claim 7
Dependent Claim
24 words
A control system as set forth in claim 4 wherein said gain-control means includes an amplifier adapted to operate in a forward AGC mode.
Claim 8
Dependent Claim
231 words
In a television receiver adapted to receive VHF, UHF and CATV signals and having a direct-access tuning system including a VHF local oscillator, a UHF local oscillator, a prescaler for counting and dividing-down the local oscillator signals to develop lower frequency oscillator signals for further processing by the tuning system, a control system for automatically adjusting the amplitude of the oscillator signals to a predetermined amplitude range within which the prescaler is adapted to count, comprising: a diplexer for receiving the VHF and UHF oscillator signals and for combining said signals to generate a single RF signal; a gain-controlled amplifier receiving a control signal and the RF signal for amplifying the RF signal as a function of the value of the control signal; a second amplifier receiving the amplified RF signal for further amplification thereof; means receiving the amplified RF signal from said second amplifier for generating the control signal such that the value thereof is representative of the difference between the amplitude of the amplified RF signal and the prescaler's amplitude range; means for applying the control signal to said gain-controlled amplifier to adjust its gain such that the RF signal output of said second amplifier has an amplitude within the predetermined amplitude range of the prescaler irrespective of the frequency of the RF signal; and means for applying the RF signal output of said second amplifier to the prescaler.
Claim 9
Dependent Claim
231 words
In a television receiver adapted to receive VHF, UHF and CATV signals and having a direct-access tuning system including a VHF local oscillator, a UHF local oscillator, a prescaler for counting and dividing-down the local oscillator signals to develop lower frequency oscillator signals for further processing by the tuning system, a control system for automatically adjusting the amplitude of the oscillator signals to a predetermined amplitude range within which the prescaler is adapted to count, comprising: a diplexer for receiving the VHF and UHF oscillator signals and for combining said signals to generate a single RF signal; a gain-controlled amplifier receiving a control signal and the RF signal for amplifying the RF signal as a function of the value of the control signal; a second amplifier receiving the amplified RF signal for further amplification thereof; means receiving the amplified RF signal from said second amplifier for generating the control signal such that the value thereof is representative of the difference between the amplitude of the amplified RF signal and the prescaler's amplitude range; means for applying the control signal to said gain-controlled amplifier to adjust its gain such that the RF signal output of said second amplifier has an amplitude within the predetermined amplitude range of the prescaler irrespective of the frequency of the RF signal; and means for applying the RF signal output of said second amplifier to the prescaler.
Claim 10
Dependent Claim
31 words
A control system as set forth in claim 6 wherein said control signal generating means includes a detector for detecting the amplitude of the RF signal output of said second amplifier.
Claim 11
Dependent Claim
17 words
A control system as set forth in claim 7 wherein said detector includes a hot carrier diode.
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) | 1984-01-13 | 1984-07-14 | 1985-01-13 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1988-01-13 | 1988-07-14 | 1989-01-13 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1992-01-13 | 1992-07-14 | 1993-01-13 | $7700.00 | Window Closed / Lapsed |