US4053713A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Multi-channel multiplex data transmission system
Assignee: Oki Electric Industry Co Ltd
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Filing: 1976-02-02
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Granted: 1977-10-11
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Expires: 1996-02-02
Abstract
Abstract The sum and difference signals of a pair of data channels are applied to a pair of roll-off filters, respectively. The outputs of said roll-off filters are modulated by a pair of carrier signals which have the phase difference (π/2) to each other. The modulated signals are added to each other in an adder and a single output signal is provided from the output of said adder. Said output signal and another output signal relating to another pair of data channels, and some pilot signals are applied to an adder, the output of which is transmitted to a receiving station in the form of a multi-channel multiplex data signal. At the receiving station, the received signal is demodulated with the inverse process of the above modulation steps and the demodulated data signals are applied to an automatic equalizer. The present invention described above provides high speed data transmission through a narrow-band-line which has only almost the Nyquist band width.
Inventors
- 👤 Kazuhiko Nitadori
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 20:18
CPC Classifications
H; H04; H04L; H04L5/00; H04L5/02; H04L5/06
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
237 words
A mutli channel multiplex orthogonal VSB transmission system comprising a modulator, a demodulator and a transmission means arranged between the modulator and the demodulator; said modulator comprising at least a two-channel modulator, means for generating a plurality of carrier waves at the frequency interval f c where f c is the pulse repetition frequency in each channels; and wherein said two-channel modulator comprises; means connected to each input channel for obtaining the sum and the difference of PAM signals of each pair of input channels, a pair of roll-off filters connected to the output of said means for the sum and the difference respectively, said roll-off filters having the equal amplitude roll-off characteristic less than 50%, a predetermined equal fixed delay and the phase characteristics of 45% and -45° respectively in the amplitude roll-off region, a variable phase shifter for shifting the phase of said carrier waves, a fixed phase shifter for delaying the phase of the output of said variable phase shifter by 90°, a first multiplying means inputs of which being connected to the output of one of said roll-off filters and the output of said fixed phase shifter, a second multiplying means inputs of which being connected to the output of the other roll-off filter and the output of said variable phase shifter, and means for adding the outputs of said first and second multiplying means and providing the output of the two-channel modulator.
Claim 2
Dependent Claim
237 words
A mutli channel multiplex orthogonal VSB transmission system comprising a modulator, a demodulator and a transmission means arranged between the modulator and the demodulator; said modulator comprising at least a two-channel modulator, means for generating a plurality of carrier waves at the frequency interval f c where f c is the pulse repetition frequency in each channels; and wherein said two-channel modulator comprises; means connected to each input channel for obtaining the sum and the difference of PAM signals of each pair of input channels, a pair of roll-off filters connected to the output of said means for the sum and the difference respectively, said roll-off filters having the equal amplitude roll-off characteristic less than 50%, a predetermined equal fixed delay and the phase characteristics of 45% and -45° respectively in the amplitude roll-off region, a variable phase shifter for shifting the phase of said carrier waves, a fixed phase shifter for delaying the phase of the output of said variable phase shifter by 90°, a first multiplying means inputs of which being connected to the output of one of said roll-off filters and the output of said fixed phase shifter, a second multiplying means inputs of which being connected to the output of the other roll-off filter and the output of said variable phase shifter, and means for adding the outputs of said first and second multiplying means and providing the output of the two-channel modulator.
Claim 3
Dependent Claim
111 words
A multi-channel multiplex orthogonal VSB transmission system according to claim 1, wherein said demodulator comprises; means for re-generating a receiving carrier wave from a received carrier wave, means for generating a demodulation carrier wave by using a variable phase shifter or a voltage controlled oscillator having the center frequency equal to the receiving carrier wave, a plurality of multiplying means for multiplying the input signals with the demodulation carrier waves, a plurality of roll-off filters the input of which being connected to the outputs of the multiplying means, and means for providing the sum and the difference of the two outputs of said roll-off filters and for providing a demodulated signal.
Claim 4
Dependent Claim
80 words
A demodulator according to claim 2, further comprising means for controlling the phase of said demodulation carrier wave, said means comprises means for detecting the polarity of a pair of demodulated signals, a pair of multiplying means for multiplying the output of the detecting means with the other demodulated signal, means for providing the difference between two outputs of said pair of multiplying means, and a low pass filter connected to the output of said means for providing the difference.
Claim 5
Dependent Claim
190 words
A multi-channel multiplex orthogonal VSB transmission system according to claim 1, further comprising a sampling circuit, said sampling circuit comprises a sampling pulse generation circuit having a band-pass filter (51) of center frequency f c /2 connected to a demodulated signal, a square circuit (52) connected to the output of said band pass filter, a second band-pass filter (53) of center frequency f c connected to the output of said square circuit (53), and a phase-controlled oscillator (54) connected to the output of said second band pass filter; a plurality of delay circuits (45 1 , 45 2 , 45 3 , 45 4 ) for delaying the sampled signal; a multiplying means (48) for multiplying the signal from the center tap of said delay circuits with the sum of the signals from the another taps of said delay circuits; a smoothing means (49, 50) connected to the output of said multiplying means; a phase shifter (43) for shifting the phase of the sampling pulse according to the output of said smoothing means; and means (42) for sampling an input signal according to the output of said phase shifter (43).
Claim 6
Dependent Claim
126 words
A multi-channel multiplex orthogonal VSB transmission system according to claim 1, further comprising an automatic equalizer the input of which being connected to the output of the sampling means (42), said automatic equalizer comprises a plurality of transversal filters (61 1 -61 10 ) provided three sets for each internal channels and two sets for the end channels; an adder (62 1 -62 4 ) for adding the outputs of said transversal filters for each channel; a decision circuit (63 1 -63 4 ) for quantizing the output of said adder; an error detecting circuit (64 1 -64 4 ) for detecting the error in the quantization; and means for changing the amplitude of said error and for changing the weight coefficients of said transversal filters.
Claim 7
Dependent Claim
116 words
A multi-channel multiplex orthogonal VSB transmission system according to claim 1, further comprising an automatic equalizer the input of which being connected to the output of the sampling means (42), said automatic equalizer comprises a transversal filter (61 1 , 61 4 , 61 7 , 61 10 ) provided for each channel; a decision circuit (63 1-63 4 ) for quantizing the output of said transversal filter; an error detecting circuit (64 1 -64 4 ) for detecting the error in the quantization; and means for changing the amplitude of said error and for changing the coefficient of said transversal filter, the phase of the demodulation carrier wave and the timing of a sampling pulse.
Claim 8
Dependent Claim
83 words
The invention as defined in claim 6, further comprising means (75 1 , 75 2 ) for changing the phase of the demodulation carrier wave, comprising a correlation means for calculating the correlation between one of the demodulated signals having the common carrier wave and the error signal of the other demodulated signal, a transversal filter connected to one of the inputs of said correlaton means, and the phase of the demodulation carrier wave being changed by the output by said correlation means.
Claim 9
Dependent Claim
82 words
The invention as defined in claim 6, further comprising means (76 1 , 76 2 ) for changing the timing of a sampling pulse, comprising a correlation means for calculating the correction between one of the sequential demodulated signals having the common carrier wave and the error signal of the other demodulated signal, a transversal filter connected to one of the inputs of said correlation means, and the timing of a sampling pulse being changed by the output of said correlation means.
Claim 10
Dependent Claim
73 words
The invention as defined in claim 6, further comprising means (61 1 , 61 10 ) for changing the timing of a sampling pulse, comprising a correlation means for calculating the correlation between the demodulated signal of an end channel and the error signal, a transversal filter connected to one of the inputs of said correlation means, and the timing of a sampling pulse being changed by the output of said correlation means.
Claim 11
Dependent Claim
43 words
A multi-channel multiplex orthogonal VSB transmission system according to claim 1, further including said modulator comprising a plurality of said two channel modulators and means for summing the output of said plurality of two channel modulators and providing the output of said modulator.
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) | 1980-10-10 | 1981-04-11 | 1981-10-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-10-10 | 1985-04-11 | 1985-10-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-10-10 | 1989-04-11 | 1989-10-11 | $7700.00 | Window Closed / Lapsed |