Pulse or digital communications – Spread spectrum – Direct sequence
Patent
1985-07-18
1987-02-24
Safourek, Benedict V.
Pulse or digital communications
Spread spectrum
Direct sequence
371 67, 3401462, 375116, H04L 704
Patent
active
046463283
ABSTRACT:
A frame alignment loss and recovery device for a digital signal carrying a frame alignment N-bit word comprises an (N+2)-stage shift register receiving the digital signal at a timing frequency H, a buffer register for extracting (N+2)-bit words from the shift register at a frequency H/3, a logic circuit for comparing each extracted word with three predetermined (N+2)-bit words respectively including N last bits, N central bits and N first bits identical to the alignment word bits in the signal, and a circuit for deriving a frame synchronization pulse in phase with the start of an alignment word contained in an extracted word having bits respectively identical to like-ranked bits in one of the three predetermined words. Because searching for the alignment word is at a frequency H/3, the logic circuit can include conventional PROM memories and alignment word errors can be tolerated despite a digital signal of high rate, for example, 34 Mbit/s.
REFERENCES:
patent: 3463911 (1969-08-01), Dupraz
patent: 3678200 (1972-07-01), Clark
patent: 4017684 (1977-04-01), Kurihara et al.
patent: 4205302 (1980-05-01), Giodo
patent: 4346475 (1982-08-01), Alexis
Chin Stephen
Safourek Benedict V.
Societe Anonyme de Telecommunications
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