Multipoint modem system having fast synchronization
US4847880A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 18, 1988 |
| Grant date | Jul 11, 1989 |
| Priority date | — |
| Expiry date | Aug 18, 2008 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L7/0029
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
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).
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.