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Machine translation
1. (WO1981000798) TIMING ACQUISITION IN VOICEBAND DATA SETS
Latest bibliographic data on file with the International Bureau   

Pub. No.:    WO/1981/000798    International Application No.:    PCT/US1980/001082
Publication Date: 19.03.1981 International Filing Date: 25.08.1980
IPC:
H04L 27/01 (2006.01), H04L 7/02 (2006.01), H04L 7/04 (2006.01)
Applicants:
Inventors:
Priority Data:
75646 14.09.1979 US
Title (EN) TIMING ACQUISITION IN VOICEBAND DATA SETS
(FR) DUREE D'ACQUISITION DANS DES ENSEMBLES DE DONNEES EN BANDES VOCALES
Abstract: front page image
(EN)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 acquisition equalizer outputs. The time by which the operation of the sampling circuitry is to be advanced or retarded is determined as a trigonometric function of two successive ones of the timing acquisition equalizer outputs. The timing acquisition signal is illustratively a double-dotting pattern having a four-symbol-interval period. That period is integrally related to the carrier frequency. This allows the samples needed in order to begin forming the timing acquisition equalizer outputs to be generated by replicating the samples taken over only four symbol intervals.
(FR)Dans un systeme de communication de donnees a multi-points utilisant une modulation a quadrature d'amplitude, un modem principal (20) et une pluralite de modems tributaires (11a, 11b...11n) sont interconnectes via des canaux de transmission respectifs (13a, 13b... 13n, 16). Un circuit egaliseur d'adaptation (55, 56) dans le modem principal egalise le canal a partir d'un modem tributaire particulier en multipliant des echantillons de signaux recus du tributaire par un ensemble de coefficients de reglage associes au tributaire. Les ensembles de coefficients de reglage pour chaque tributaire sont stockes dans une memoire (91) d'ou ils sont extraits au debut de la transmission a partir de ce tributaire. Un circuit de duree-acquisition (29) dans le modem principal ajuste la phase du circuit d'echantillonnage (23, 27) de ce dernier au debut d'une transmission a partir d'un tributaire donne de sorte que les signaux recus sont echantillonnes aux points de temps corrects. En particulier, un signal de duree-acquisition ayant des composants spectraux seulement dans la region de non augmentation d'amortissement de la fonction transfert equivalente a la bande de base egalisee est transmis par le tributaire. Le principal echantillonne et egalise le signal recu de duree-acquisition pour former une succession de sorties d'egalisation de duree-acquisition. Le fonctionnement du circuit d'echantillonnage doit etre avance ou retarde d'un temps qui est determine comme une fonction trigonometrique de deux sorties successives des sorties d'egalisation de duree-acquisition. Le signal de duree-acquisition est une configuration a double points ayant une periode d'intervalle a quatre symboles. Cette periode est une fonction integrale de la frequence porteuse. Ceci permet d'avoir les echantillons necessaires pour commencer la formation des sorties d'egalisation de duree-acquisition a generer en reproduisant les echantillons pris sur seulement quatre intervalles de symboles.
Designated States:
Publication Language: English (EN)
Filing Language: English (EN)