Patent US3562420A successfully refreshed from Google Patents.
US3562420A
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Pseudo random quantizing systems for transmitting television signals
Assignee: Post Office
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Filing: 1968-03-12
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Granted: 1971-02-09
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Expires: 1988-03-12
Abstract
Abstract A pseudo-random quantizing system for television signals comprises a PCM transmission channel which includes a multilevel quantizer, and also includes means for generating a multilevel dither signal produced from pseudo-random binary noise signals and arranged to give a nonwhite predominantly high frequency power spectrum which is matched to the noise sensitivity characteristic of the viewer.
Inventors
- 👤 John E Thompson
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-03 12:52
CPC Classifications
H; H04; H04B; H04B14/00; H04B14/02; H04B14/04; H04B14/046; H04N; H04N19/00; H04N19/90
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
161 words
A pseudorandom quantizing system for use with a sampled video input signal, said system comprising: a PCM video transmission channel including a multilevel quantizer for converting an analogue input to digital form and then back again to an analogue output; dither signal generator means for producing a multilevel dither signal; means in advance of said quantizer for adding said dither signal to said sampled video input signal; means following said quantizer for subtracting a signal equivalent to said dither signal from said analogue output of said quantizer; means for synchronizing said dither generator means with said sampled video input signal; said dither signal generator means comprising: means for producing pseudorandom binary noise signals; and a weighting network for weighting said pseudorandom binary noise signals to provide a multilevel dither signal which is autocorrelated to provide a power spectrum of increasing power density toward the higher frequency end of the frequency band of the video signal at the output of said system.
Claim 2
Dependent Claim
161 words
A pseudorandom quantizing system for use with a sampled video input signal, said system comprising: a PCM video transmission channel including a multilevel quantizer for converting an analogue input to digital form and then back again to an analogue output; dither signal generator means for producing a multilevel dither signal; means in advance of said quantizer for adding said dither signal to said sampled video input signal; means following said quantizer for subtracting a signal equivalent to said dither signal from said analogue output of said quantizer; means for synchronizing said dither generator means with said sampled video input signal; said dither signal generator means comprising: means for producing pseudorandom binary noise signals; and a weighting network for weighting said pseudorandom binary noise signals to provide a multilevel dither signal which is autocorrelated to provide a power spectrum of increasing power density toward the higher frequency end of the frequency band of the video signal at the output of said system.
Claim 3
Dependent Claim
35 words
A pseudorandom quantizing system as in claim 1 wherein: said means for producing pseudorandom binary noise signals comprises a shift register for supplying pseudorandom binary noise signals from adjacent stages thereof to said weighting network.
Claim 4
Dependent Claim
16 words
A pseudorandom quantizing system as claimed in claim 2, wherein said shift register comprises eleven stages.
Claim 5
Dependent Claim
64 words
A pseudorandom quantizing system as in claim 1, wherein said dither signal generator means comprises: a shift register for providing pseudorandom binary noise signals and a square wave generator for providing a binary signal having an amplitude equal to half of one quantizing step and which, with respect to each sampled area of a picture being transmitted, averages to zero over two successive frames.
Claim 6
Dependent Claim
56 words
A pseudorandom quantizing system as in claim 4, wherein said synchronizing means comprises: an oscillator for clocking said shift register at a predetermined frequency; and wherein said square wave generator provides square waves having a frequency of the order of half of the shift register clock frequency and synchronized to average to zero over two frames.
Claim 7
Dependent Claim
57 words
A pseudorandom quantizing system as in claim 5, wherein: the video input signal is a television signal having a predetermined line frequency; and said frequency of said square wave is equal to an odd multiple of one-half of the line frequency and is alternately advanced and retarded in phase by 90* at the initiation of each frame.
Claim 8
Dependent Claim
64 words
A pseudorandom quantizing system as in claim 1, wherein said generator means comprises: a shift register; means for clocking said shift register at a first frequency to generate relatively low frequency pseudorandom binary noise; and modulating means for modulating said relatively low-frequency noise with signals at said first Frequency and with signals at a second frequency to provide instant signals for said weighting network.
Claim 9
Dependent Claim
21 words
A pseudorandom quantizing system as in claim 7, wherein said first and second frequencies are 1.5 MHz. and 3 MHz. respectively.
Claim 10
Dependent Claim
75 words
A pseudorandom quantizing system as claimed in claim 7, including: output junction means in three stages of said shift register operatively connected to said weighting network; the signal on one of said output junction means being modulated at said first frequency; the signal on the second of said output junction means being modulated at said second frequency; and the signal on the third of said output junction means being connected directly to said weighting network.
Claim 11
Dependent Claim
52 words
A pseudorandom quantizing system as in claim 1, including: a preemphasis filter network connected at an input to said means for adding a dither signal; and a deemphasis filter network connected at an output of said means for subtracting a signal equivalent to said dither signal from the output of said quantizer.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1974-02-08 | 1974-08-10 | 1975-02-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1978-02-08 | 1978-08-10 | 1979-02-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1982-02-08 | 1982-08-10 | 1983-02-09 | $7700.00 | Window Closed / Lapsed |