US3626090A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Automatic phase control system for use in suppressed carrier television transmission
Assignee: NEC Corp
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Filing: 1970-03-02
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Granted: 1971-12-07
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Expires: 1990-03-02
Abstract
Abstract An automatic phase control system specially adapted for use in receiving and demodulating television signals which are transmitted with the carrier effectively suppressed. The automatic phase control system includes a carrier wave generator whose phase is either maintained or reversed by 180*. The need for phase reversal is determined by combining the received television signal with the synchronized carrier and performing amplitude comparison between the superimposed signals and the synchronized carrier to generate an output control signal whenever the amplitude of the superimposed signals is lower than the amplitude of the synchronized carrier wave. This control signal is passed only during the vertical blanking period, and is applied to a phase reversal circuit coupled to the output of the synchronizing carrier wave generator so that the appropriate inphase carrier will be used to demodulate the carrier suppressed television signal.
Inventors
- 👤 Susumu Akiyama
- 👤 Mitsuaki Naganuma
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 14:25
CPC Classifications
H; H04; H04N; H04N5/00; H04N5/44; H04N5/455
Claims Analysis
Total Claims: 4
Claim 1
Independent Claim
261 words
In a suppressed carrier-wave television signal transmission system wherein said television signal includes a first synchronizing signal of first repetition period, a second synchronizing signal of a second repetition period longer than said first repetition period and a blanking signal occurring during said second repetition period is transmitted with the carrier wave substantially suppressed, and is demodulated at a receiving end by use of a synchronized carrier wave component generated at the receiving end; an automatic phase control system for a receiver for said transmission system, comprising: first means for producing said synchronized carrier wave component; second means coupled to said first means for demodulating said television signal; third means for extracting said second synchronizing information from said demodulated television signal; fourth means coupled to said third means and responsive to said second synchronizing signals and said blanking signal for producing a gate pulse; fifth means for superimposing said synchronized carrier wave component on said television signal to produce a composite signal; polarity discriminating means coupled to said first means and said fifth means and responsive to said gate pulse for determining the polarity of said synchronized carrier wave component with respect to said composite signal, to produce a polarity-representing signal only during the presence of said gate pulse; sixth means responsive to the result of phase comparison between said television signal and said synchronized carrier wave component for controlling the phase of said synchronized carrier wave component; and seventh means responsive to said polarity-representing signal for controlling the polarity of said synchronized carrier wave component generated by said fourth means.
Claim 2
Dependent Claim
261 words
In a suppressed carrier-wave television signal transmission system wherein said television signal includes a first synchronizing signal of first repetition period, a second synchronizing signal of a second repetition period longer than said first repetition period and a blanking signal occurring during said second repetition period is transmitted with the carrier wave substantially suppressed, and is demodulated at a receiving end by use of a synchronized carrier wave component generated at the receiving end; an automatic phase control system for a receiver for said transmission system, comprising: first means for producing said synchronized carrier wave component; second means coupled to said first means for demodulating said television signal; third means for extracting said second synchronizing information from said demodulated television signal; fourth means coupled to said third means and responsive to said second synchronizing signals and said blanking signal for producing a gate pulse; fifth means for superimposing said synchronized carrier wave component on said television signal to produce a composite signal; polarity discriminating means coupled to said first means and said fifth means and responsive to said gate pulse for determining the polarity of said synchronized carrier wave component with respect to said composite signal, to produce a polarity-representing signal only during the presence of said gate pulse; sixth means responsive to the result of phase comparison between said television signal and said synchronized carrier wave component for controlling the phase of said synchronized carrier wave component; and seventh means responsive to said polarity-representing signal for controlling the polarity of said synchronized carrier wave component generated by said fourth means.
Claim 3
Dependent Claim
91 words
An automatic phase control system as claimed in claim 1, wherein said fourth means comprises: a monostable multivibrator for generating output pulses in response to said synchronizing information; a delay line for delaying the output pulses of said monostable multivibrator; a logic circuit for performing an EXCLUSIVE-OR operation upon the output pulses of said monostable multivibrator and the output signal of said delay line; a low pass filter for filtering said EXCLUSIVE-OR output; and a slicing circuit for slicing the output signal of said low pass filter at a predetermined level.
Claim 4
Dependent Claim
142 words
An automatic phase control system as claimed in claim 1, wherein said polarity-discriminating means comprises: a first rectifier for rectifying said composite signal; a second rectifier for rectifying said synchronized carrier wave component; comparison means for comparing the amplitudes of the outputs of said first and second rectifiers; a gate circuit for enabling the output signal of said comparison means to pass therethrough only during the gate period of said gate signal; a low pass filter for removing high frequency components from the output of said gate circuit; a Schmitt trigger circuit controlled by the output signal from said low pass filter for generating an output of a first voltage level when the output of said low pass filter exceeds a predetermined threshold and of a second voltage level when the output of said low pass filter lies below said threshold level.
References Cited (Backward Citations)
US3057954A
Cited
US3144512A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-12-06 | 1975-06-07 | 1975-12-07 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-12-06 | 1979-06-07 | 1979-12-07 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-12-06 | 1983-06-07 | 1983-12-07 | $7700.00 | Window Closed / Lapsed |