US4847880A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Multipoint modem system having fast synchronization
Assignee: NCR Voyix Corp
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Filing: 1988-08-18
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Granted: 1989-07-11
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Expires: 2008-08-18
Abstract
Abstract A multipoint data modem communication system (10) includes a master modem (12) and a plurality of remote modems (14, 16 and 18). During an initial, remote-to-master transmission, a relatively long training sequence is transmitted and receiver parameter and equalizer coefficients are stored in a storage unit (156) in the master modem (12). During subsequent transmissions a relatively short training sequence which synchronizes the master modem receiver timing and also identifies the transmitting remote modem is applied. In the master modem an interpolation filter based on a ninth order Lagrange interpolation formula is located between an analog-to-digital converter (84) and a band-pass filter (92). Coefficients for the interpolation filter are calculated using a residual time shift value which is computed using a DFT calculator (96) which is coupled to a phase segment detector (142) and a phase-to-time-shift converter (146).
Inventors
- 👤 Adriaan Kamerman
- 👤 Timothy N. Doolittle
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 17:20
CPC Classifications
H; H04; H04L; H04L7/00; H04L7/04; H04L7/10; H04L27/00; H04L27/01; H04L7/0016; H04L7/002; H04L7/0029
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
144 words
A multipoint data modem communication system having a master modem coupled over a transmission line to a plurality of remote modems including: a modem receiver mounted in said master modem; sampling means mounted in said modem receiver adapted to receive analog signals from the transmission line; timing recovery means mounted in the modem receiver for supplying timing signals to said sampling means; interpolation filter means in said modem receiver having an input coupled to an output of said sampling means and an output coupled to an input of said timing recovery means; and filter coefficient calculation means mounted in said modem receiver, coupled to said interpolation filter means, and adapted to calculate, in accordance with a predetermined interpolation formula, filter coefficients for said interpolation filter means during the reception by said receiver means of a training signal transmitted by one of said remote modems.
Claim 2
Dependent Claim
144 words
A multipoint data modem communication system having a master modem coupled over a transmission line to a plurality of remote modems including: a modem receiver mounted in said master modem; sampling means mounted in said modem receiver adapted to receive analog signals from the transmission line; timing recovery means mounted in the modem receiver for supplying timing signals to said sampling means; interpolation filter means in said modem receiver having an input coupled to an output of said sampling means and an output coupled to an input of said timing recovery means; and filter coefficient calculation means mounted in said modem receiver, coupled to said interpolation filter means, and adapted to calculate, in accordance with a predetermined interpolation formula, filter coefficients for said interpolation filter means during the reception by said receiver means of a training signal transmitted by one of said remote modems.
Claim 3
Dependent Claim
21 words
A multipoint data modem communication system according to claim 1 wherein said filter coefficient calculation means utilizes a Lagrange interpolation formula.
Claim 4
Dependent Claim
50 words
A multipoint data modem communication system according to claim 2 in which said modem receiver includes a plurality of first multipliers and in which said interpolation filter means includes a plurality of first buffer shift register stages having outputs coupled to said multipliers to which said filter coefficients are applied.
Claim 5
Dependent Claim
51 words
A multipoint data modem communication system according to claim 3 in which said modem receiver includes a band-pass filter means whose output is connected to a data signal development means and in which the output of said interpolation filter means is coupled to the band-pass filter means for developing data signals.
Claim 6
Dependent Claim
48 words
A multipoint data modem communication system according to claim 4 in which said modem receiver further includes a second multiplier and said band-pass filter means includes a plurality of second buffer shift register stages having outputs coupled to said further multipliers to which band-pass filter coefficients are applied.
Claim 7
Dependent Claim
58 words
A multipoint data modem communication system according to claim 2, wherein said Lagrange interpolation formula corresponds to a ninth order interpolation, and wherein ##EQU5## where K=-4, . . . ,0, . . . , +4, where A k (p) represents the value of k'th one of said interpolation filter coefficients; and where p is a time shift value.
Claim 8
Dependent Claim
77 words
A multipoint data modem communication system according to claim 6, wherein said filter coefficient calculation means includes Discrete Fourier Transform (DFT) calculation means adapted to effect Discrete Fourier Transform calculations, a phase segment detector coupled to said DFT calculation means and adapted to detect the phase value of the output of said DFT calculations means and phase-to-time-shift conversion means coupled to an output of said phase-to-time-shift conversion means and adapted to calculate said time shift value p.
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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) | 1992-07-10 | 1993-01-09 | 1993-07-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-07-10 | 1997-01-09 | 1997-07-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-07-10 | 2001-01-09 | 2001-07-11 | $7700.00 | Window Closed / Lapsed |