Timing acquisition in voiceband data sets
US4245345A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 14, 1979 |
| Grant date | Jan 13, 1981 |
| Priority date | — |
| Expiry date | Sep 14, 1999 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH04L7/046
- WIPO fieldDigital communication
- WIPO sectorElectrical engineering
Abstract
In a multipoint data communication system using quadrature-amplitude modulation, a master modem (20) and a plurality of tributary modems (11a, 11b . . . 11n) are interconnected via respective transmission channels (13a, 13b . . . 13n, 16). Adaptive equalizer circuitry (55, 56) in the master modem equalizes the channel from a particular tributary by multiplying samples of signals received from the tributary by an ensemble of tap coefficients associated with the tributary. The tap coefficient ensembles for each tributary are stored in a memory (91) from which they are retrieved at the start of transmission from that tributary. Timing-acquisition circuitry (29) within the master modem adjusts the phase of the latter's sampling circuitry (23, 27) at the start of transmission from a given tributary so that the received signals are sampled at the correct time points. In particular, a timing acquisition signal having spectral components only within the non-rolloff region of the equalized baseband-equivalent transfer function is transmitted by the tributary. The master samples and equalizes the received timing acquisition signal to form a succession of timing acquisiton equalizer outputs. …
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.