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Patent US3733550A successfully refreshed from Google Patents.
US3733550A
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Multilevel signal transmission system
Assignee: NTT Inc
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Filing: 1972-04-20
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Granted: 1973-05-15
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Expires: 1992-04-20
Abstract
Abstract Apparatus is disclosed for transmitting a multilevel signal together with at least one pilot signal of specified frequency as a timing signal for determining the sampling position of a transmitted signal and/or a signal for reproducing a demodulating carrier. Further, a reference level signal of a predetermined level is inserted in the multilevel signal train and the pilot signals are inserted in the multilevel signal train after frequency components in the neighborhood of the specified frequencies of the pilot signals are removed from the multilevel signal train on the transmitted side of the transmission line. In processing the multilevel signals the deviation of a sampled transmitted level of the reference level signal from the predetermined level thereof is detected; next, the frequency components in the vicinity of the pilot signals of the specified frequencies removed on the transmitting side of the line are extracted from the deviation; and then the signal distortion of the multilevel signal is corrected with the extracted frequency components on the receiving side on the transmission line.
Inventors
- 👤 K Tazaki
- 👤 H Yamamoto
- 👤 S Hinoshita
- 👤 S Hagiwara
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 20:35
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/02; H04L27/08
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
184 words
Apparatus for transmitting a multilevel signal having at least one pilot signal of specified frequency incorporated therein over a transmission line having input and output terminals, said apparatus comprising: transmission means coupled to the input terminal of the transmission line, said transmission means including reference means for providing a reference level signal of a predetermined level and for inserting the reference level signal in a train of the multilevel signal, means for removing frequency components of the multilevel signal adjoining the specified frequency of the pilot signal, and means for providing and inserting the pilot signal of the specified frequency into the multilevel signal from which the frequency components have been removed; and receiving means coupled to the output terminal of the transmission line, said receiving means including detection means for detecting the error between the level of the transmitted reference level signal and the predetermined level, means for deriving the frequency components adjoing the specified frequency of the pilot signal from the detected error, and correction means for removing signal distortion from the transmitted multilevel signal in response to the derived frequency components.
Claim 2
Dependent Claim
184 words
Apparatus for transmitting a multilevel signal having at least one pilot signal of specified frequency incorporated therein over a transmission line having input and output terminals, said apparatus comprising: transmission means coupled to the input terminal of the transmission line, said transmission means including reference means for providing a reference level signal of a predetermined level and for inserting the reference level signal in a train of the multilevel signal, means for removing frequency components of the multilevel signal adjoining the specified frequency of the pilot signal, and means for providing and inserting the pilot signal of the specified frequency into the multilevel signal from which the frequency components have been removed; and receiving means coupled to the output terminal of the transmission line, said receiving means including detection means for detecting the error between the level of the transmitted reference level signal and the predetermined level, means for deriving the frequency components adjoing the specified frequency of the pilot signal from the detected error, and correction means for removing signal distortion from the transmitted multilevel signal in response to the derived frequency components.
Claim 3
Dependent Claim
40 words
Apparatus as claimed in claim 1, wherein said receiving means includes sampling means for sampling the transmitted multilevel signal at predetermined intervals, and wherein the pilot signal of the specified frequency comprises a timing signal for determining the sampling interval.
Claim 4
Dependent Claim
28 words
Apparatus as claimed in claim 2, wherein the timing signal has a frequency of one half the repetitive frequency of the multilevel signal in the multilevel signal train.
Claim 5
Dependent Claim
61 words
Apparatus as claimed in claim 1, wherein said transmission means includes means for modulating a multilevel signal to be transmitted, said receiving means includes means for demodulating the transmitted signal, and wherein the pilot signal of the specified frequency comprises a signal for reproducing the demodulating carrier to be applied to said demodulating means for demodulating the transmitted modulated multilevel signals.
Claim 6
Dependent Claim
34 words
Apparatus as claimed in claim 4, wherein the pilot signal for repRoducing the demodulating carrier is a signal of substantially zero frequency component when the multilevel signal train is considered in the base band.
Claim 7
Dependent Claim
41 words
Apparatus as claimed in claim 3, wherein said reference means provides a reference level signal having a frequency of 1/R substantially equal to the repetitive frequency of the multilevel signal in the multilevel signal train, where R is an odd number.
Claim 8
Dependent Claim
51 words
Apparatus as claimed in claim 6, wherein said reference means provides a reference level signal having at least first and second levels, and the reference level signal has a pattern repetitive frequency which is not one half the repeated frequency of insertion of the reference level signal into the multilevel signal.
Claim 9
Dependent Claim
112 words
Apparatus as calimed in claim 1, wherein said transmission means includes: storage means clock means for generating a first, repetitive clock signal of intervals of T/m where T is a predetermined interval integer of time and m is a predetermined interger and for generating a second, repetitive clock signal at an interval of T/(m+1); means responsive to the first clock signal for storing the multilevel signal in said storage means; means responsive to the second clock signal for retrieving from said storage means a train of the multilevel signal; means for inserting at the time intervals of T the reference level signal into the train multilevel signals retrieved from said storage means.
Claim 10
Dependent Claim
65 words
Apparatus as calimed in claim 8, wherein each level of the multilevel signals to be transmitted is represented by a binary number of n''s bits, where n is a predetermined interger, said transmission means including means for providing the level of the reference level signal of a selected magnitude at the transition point of the binary digit of a selected position of the n''s bits.
Claim 11
Dependent Claim
37 words
Apparatus as claimed in claim 9, wherein said detection means detects the error difference between the level of the transmitted reference level signal and the predetermined level as determined by the binary digit of the selected position.
Claim 12
Dependent Claim
113 words
Apparatus as claimed in claim 10, wherein said receiving means includes demodulator means for converting a binary digit component of the selected position of the transmitted multilevel signal train into a signal having a frequency component of substantially zero, extracting means for sampling the demodulated signal with the period T, filter means coupled to said extracting means for removing the high frequency component of the signal derived therefrom, and modulator means for modulating the pilot signal of the specified frequency in accordance with the output signal derived from said filter means, said correction means responsive to the output signal of said modulator means for correcting signal distortion in the transmitted multilevel signal train.
Claim 13
Dependent Claim
85 words
Apparatus as claimed in claim 10, wherein said receiving means includes extracting means for sampling at repetitive intervals of the period T, the binary digit of the selected position of the transmitted multilevel signal train, bandpass filter means for removing from the sampled multilevel signal train a frequency band having a center frequency substantially equal to the specified frequency of the pilot signal, said adjustment means responsive to the output signal of said filter means for correcting signal distortion in the transmitted multilevel signal train.
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) | 1976-05-14 | 1976-11-13 | 1977-05-15 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-05-14 | 1980-11-13 | 1981-05-15 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-05-14 | 1984-11-13 | 1985-05-15 | $7700.00 | Window Closed / Lapsed |