US3688019A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Demodulator circuit for color television-receiver
Assignee: US Philips Corp
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Filing: 1970-01-23
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Granted: 1972-08-29
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Expires: 1990-01-23
Abstract
Abstract A phase control circuit for a demodulator circuit for a PAL receiver, wherein with the aid of the output signals of two synchronous demodulators each of which signals of two synchronous demodulators each of which demodulate a quadrature component from the PAL chrominance signal a phase correction signal dependent on the differential phase error is obtained after filtering and multiplication, division or similar non-linear handling for the purpose of correcting the phase of the axes of the PAL chrominance signal to be demodulated relative to that of the chrominance subcarrier signal to be used for the synchronous demodulation.
Inventors
- 👤 Fritz Weitzsch
- 👤 Erich Eduard Walther
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 16:32
CPC Classifications
H; H04; H04N; H04N9/00; H04N9/44; H04N9/455
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
220 words
A demodulator circuit for demodulating the chrominance component of a color television signal of a PAL color television receiver, which chrominance signal comprises a first quadrature component of a chrominance subcarrier modulated by a first color information signal, and a second quadrature component of said subcarrier modulated by a second color information signal, said second quadrature component alternating 180* in phase between successive line periods of said color television signal, said color signal further comprising a chrominance signal reference frequency component, said demodulator circuit comprising first and second synchronous demodulator means for producing demodulated color information signals, means for applying said first and second color information signals to said demodulators as respective first signal inputs, means responsive to said reference frequency component for producing first and second demodulating signals in phase quadrature and for applying said signals as respective second signal inputs to said demodulators, non-linear signal processing means comprising a filter circuit coupled to the outputs of said demodulators for receiving said color information signals and for producing a control quantity having a value determined by the phase difference between the respective first and second signals applied to said demodulators irrespective of said phase alterations, and means responsive to said control quantity for modifying the phase relationship between the chrominance signal respectively the demodulation signals applied to said demodulators.
Claim 2
Dependent Claim
220 words
A demodulator circuit for demodulating the chrominance component of a color television signal of a PAL color television receiver, which chrominance signal comprises a first quadrature component of a chrominance subcarrier modulated by a first color information signal, and a second quadrature component of said subcarrier modulated by a second color information signal, said second quadrature component alternating 180* in phase between successive line periods of said color television signal, said color signal further comprising a chrominance signal reference frequency component, said demodulator circuit comprising first and second synchronous demodulator means for producing demodulated color information signals, means for applying said first and second color information signals to said demodulators as respective first signal inputs, means responsive to said reference frequency component for producing first and second demodulating signals in phase quadrature and for applying said signals as respective second signal inputs to said demodulators, non-linear signal processing means comprising a filter circuit coupled to the outputs of said demodulators for receiving said color information signals and for producing a control quantity having a value determined by the phase difference between the respective first and second signals applied to said demodulators irrespective of said phase alterations, and means responsive to said control quantity for modifying the phase relationship between the chrominance signal respectively the demodulation signals applied to said demodulators.
Claim 3
Dependent Claim
43 words
A demodulator circuit as claimed in claim 1, further comprising means for Reversing the phase of the output signal of one of said demodulators at a rate equal to one-half of the frequency of the line scanning frequency of said color television signal.
Claim 4
Dependent Claim
20 words
A demodulator circuit as claimed in claim 2, characterized in that the non-linear signal processing circuit is a multiplier circuit.
Claim 5
Dependent Claim
25 words
A demodulator circuit as claimed in claim 2, further comprising a lowpass filter interposed between said non-linear signal processing circuit and said phase modifying means.
Claim 6
Dependent Claim
36 words
A demodulator circuit as claimed in claim 4, characterized in that the cut-off frequency of the lowpass filter between the non-linear signal processing circuit and the phase modifying means is between 1 Hz and 100 Hz.
Claim 7
Dependent Claim
71 words
A demodulator circuit as claimed in claim 3 wherein the said multiplier circuit comprises a first and second gating circuit each having two inputs and an output, the two inputs of each gating circuit being coupled to the outputs of the demodulators, one input in phase with the corresponding input of the other gating circuit and the other input in opposite phase with the corresponding input of the other gating circuit.
Claim 8
Dependent Claim
19 words
A demodulator circuit as claimed in claim 2, characterized in that the non-linear handling circuit is a quotient-forming circuit.
Claim 9
Dependent Claim
89 words
A demodulator circuit as claimed in claim 7, wherein the said quotient-forming circuit comprises two logarithmic circuits an input of each of which is coupled to an input of the quotient-forming circuit and an output is coupled to an input of a difference-producing circuit, an output of which difference producing circuit is coupled at least through an anti-logarithmic circuit to the phase correction circuit, while a polarity correction circuit is coupled to the inputs of the logarithmic circuits and to the control signal input of the phase correction circuit.
Claim 10
Dependent Claim
26 words
A demodulator circuit as claimed in claim 1 wherein said phase relationship modifying means is interposed between said means for producing demodulating signals and said demodulators.
Claim 11
Dependent Claim
40 words
A demodulator circuit as claimed in claim 2 further comprising gating means interposed between the output of said demodulating means and said non-linear signal processing circuit, and means for energizing said gating means by a pulse signal of line frequency.
Claim 12
Dependent Claim
25 words
A demodulator circuit as claimed in claim 10 further comprising a delay circuit interposed between said gating means and the source of line frequency pulses.
Claim 13
Dependent Claim
38 words
A demodulator circuit as claimed in claim 11, characterized in that the delay circuit is coupled to a low-frequency signal generator, having a frequency in the range of 0.5 to 15 Hz for obtaining a periodically varying delay.
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) | 1975-08-29 | 1976-02-28 | 1976-08-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-08-29 | 1980-02-28 | 1980-08-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-08-29 | 1984-02-28 | 1984-08-29 | $7700.00 | Window Closed / Lapsed |