US3727136A
Expired / Lapsed
US
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Automatic equalizer for phase-modulation data transmission systems
Assignee: AT&T Inc
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Filing: 1971-11-17
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Granted: 1973-04-10
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Expires: 1991-11-17
Abstract
Abstract An adaptive transversal equalizer for phase-modulated data transmission systems employs a tapped delay line provided with separate in-phase and quadrature sets of weighting attenuators operating on time spaced samples of passband signals appearing at each tap. The two sets of selectively attenuated tap signals are then combined to form the equalized output signal. Control signals for adjusting the respective sets of weighting attenuators according to a zero-forcing algorithm are derived solely from the phase differences among adjacent and nonadjacent received signal samples.
Inventors
- 👤 H Schroeder
- 👤 J Sheehan
- 👤 R Tracey
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 10:50
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/01
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
216 words
In combination with a synchronous phase-modulation data transmission system, an automatic adaptive transversal equalizer comprising a delay line with synchronously spaced taps therealong accepting at an input data signal received from said system, a first and second set of adjustable attenuators at each of said taps, means for combining the outputs of said first set of attenuators in quadrature with the outputs of said second set of attenuators to form an equalized passband received signal, means for demodulating the phase angle changes between adjacent synchronous samples of said equalized signal, said phase angle changes representing first demodulated data signals and the departure of a demodulated phase angle change from predetermined discrete phase angle changes constituting an error signal, means for storing a plurality of first data signals from said demodulating means, means for summing pairs of said first data signals from said storing means to obtain a plurality of second data signals representing nonadjacent phase angle changes, means for converting said first and second data signals into sine and cosine signals representing the sine and cosine values of demodulated phase angle changes, and means for correlating respective sine and cosine signals with said error signal to provide control signals for adjusting said first and second sets of attenuators in a direction to minimize said error signal.
Claim 2
Dependent Claim
216 words
In combination with a synchronous phase-modulation data transmission system, an automatic adaptive transversal equalizer comprising a delay line with synchronously spaced taps therealong accepting at an input data signal received from said system, a first and second set of adjustable attenuators at each of said taps, means for combining the outputs of said first set of attenuators in quadrature with the outputs of said second set of attenuators to form an equalized passband received signal, means for demodulating the phase angle changes between adjacent synchronous samples of said equalized signal, said phase angle changes representing first demodulated data signals and the departure of a demodulated phase angle change from predetermined discrete phase angle changes constituting an error signal, means for storing a plurality of first data signals from said demodulating means, means for summing pairs of said first data signals from said storing means to obtain a plurality of second data signals representing nonadjacent phase angle changes, means for converting said first and second data signals into sine and cosine signals representing the sine and cosine values of demodulated phase angle changes, and means for correlating respective sine and cosine signals with said error signal to provide control signals for adjusting said first and second sets of attenuators in a direction to minimize said error signal.
Claim 3
Dependent Claim
57 words
The combination defined in claim 1 in which said combining means comprises a first bus to which all outputs of said first set of attenuators are applied, a second bus to which all outputs of said second set of attenuators are applied, and broadband quadrature phase-shifting means in series with one of said first and second buses.
Claim 4
Dependent Claim
52 words
The combination defined in claim 1 in which said combining means comprises a bus to which all outputs of said first set of attenuators are directly connected, quadrature phase-shifting means for each output of said second set of attenuators and means for applying the outputs of said phase-shifting means to said bus.
Claim 5
Dependent Claim
155 words
The combination defined in claim 1 in which said demodulating means comprises a stable oscillator for generating a reference wave whose frequency is integrally related by a power of two to that of the carrier wave whose phase encoder data signals are to be demodulated, a frequency counter driven by said reference wave and having a plurality of stages equal in number to said power of two, the binary states of the stages thereof representing a count of the number of cycles of said reference wave incident thereon with respect to a reset condition, resetting means for said frequency counter responsive to a sampling pulse coincident with the occurrence of a zero crossing of a predetermined sense nearest the center of a data signaling interval, and readout means for storing the most significant states of said frequency counter just prior to resetting as a measure of the phase angle changes between consecutive data signaling intervals.
Claim 6
Dependent Claim
72 words
The combination defined in claim 4 in which said demodulating means further comprises a clock source providing a synchronizing pulse substantially at the center of each data signaling interval, means jointly responsive to said synchronizing pulse and a transition in a received data signal for generating a sample pulse, and gating means responsive to said sampling pulse for controlling the transmission of the reference wave from said oscillator to said frequency counter.
Claim 7
Dependent Claim
16 words
The combination defined in claim 1 in which said storing meaNs comprises a multistage shift register.
Claim 8
Dependent Claim
18 words
The combination defined in claim 1 in which each of said pair-combining means comprises a binary full adder.
Claim 9
Dependent Claim
150 words
The combination defined in claim 1 in which said converting means comprises input means for the data signal bits representing phase angle changes, first means for combining modulo-two the two most significant data signal bits to form a first control signal representative of the algebraic sign of the cosine of the angle of phase change, second means for combining the second and third most significant data signal bits to generate an inhibit signal equivalent to a zero value of the cosine of the angle of phase change, means for inverting the most significant data signal bit to form a second control signal representative of the algebraic sign of the sine of the angle of phase change, and third means for combining the inverted second and third most significant data signal bits to generate an inhibit signal equivalent to a zero value of the sine of the angle of phase change.
Claim 10
Dependent Claim
22 words
The combination defined in claim 1 in which said correlating means comprise a plurality of Exclusive-OR gates, one for each adjustable attenuator.
References Cited (Backward Citations)
US3400332A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1976-04-09 | 1976-10-09 | 1977-04-10 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1980-04-09 | 1980-10-09 | 1981-04-10 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1984-04-09 | 1984-10-09 | 1985-04-10 | $7700.00 | Window Closed / Lapsed |