Method and apparatus for phase reference recovery in high speed

Details Method and apparatus for phase reference recovery in high speed Method and apparatus for phase reference recovery in high speed

1987-08-04

1988-09-13

Safourek, Benedict V.

Pulse or digital communications

Repeaters

Testing

375 9, 375 39, 375 42, 375 78, 329 50, 329146, H03D 122

Patent

active

047714387

ABSTRACT:
A fast phase reference recovery apparatus for use in a data communication system employing a signal constellation which is variant for certain rotations which will produce local minima in the phase error signal output of a phase lock loop. The incoming signal is rotated by one or more phase shifting networks, the outputs of which are provided to constellation decision circuits for the constellation in use. One of the constellation decision circuits will be locked on to the correct local minimum and thus on to the proper phase constellation, and the others will be locked onto incorrect rotations of the constellation. The magnitudes of the errors produced by the constellation decision circuits are compared and selection of the data signals from the proper circuit is made based on the relative magnitudes of these error signals. In preferred forms, the comparison of the magnitudes of the error signals is averaged over a predetermined number of baud times to improve reliability. The apparatus is self-locking on to the proper phase reference without the use of training or synchronization sequences.

REFERENCES:
patent: 3955141 (1976-05-01), Lyon et al.
patent: 4061978 (1977-12-01), Motley et al.
patent: 4687999 (1987-08-01), Desperben et al.

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