Pulse or digital communications – Repeaters – Testing
Patent
1988-08-18
1989-07-11
Griffin, Robert L.
Pulse or digital communications
Repeaters
Testing
375 13, 375103, 375106, 375111, 36472410, H04B 138, H04L 710
Patent
active
048478806
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).
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