Augmented phase-locked loop for very wide range acquisition and method therefor

DETAILED DESCRIPTION Accordingly it is an object of the present invention to provide a new and improved phase-locked loop having a very wide, unambiguous locking range.
It is a further object to provide a new and improved phase-locked loop for extracting a data clock from the data stream provided by data communication systems using a multiple symbol encoding scheme wherein two like symbols cannot appear successively.
Another object of the present invention is to provide a new and improved method for very wide range acquisition in a phase-locked loop.
Among the advantages of the present invention are that it allows automatic unambiguous locking to the correct data rate under noisy signal conditions over a wide range of input data rates, without any constraints on the source data message and without manual intervention.
These and other objects and advantages of the present invention will become apparent to those skilled in the art upon consideration of the accompanying specification, claims and drawings.
In order to attain the above mentioned and other objects and advantages, the apparatus of the present invention involves a phase-locked loop for use with the system of data communication having a plurality of transmission channels and providing a sequence of symbol signals along the plurality of channels such that no channel is used for transmission twice in succession and such that the rising and falling transitions of a symbol signal on one of the plurality of channels respectively coincide with the falling transition of a signal on one other of the plurality of channels and the rising transition of a signal on one other of the plurality of channels.
The phase-locked loop comprises a plurality of channel inputs coupled to a plurality of inputs of means for detecting the coincidental symbol signal transitions having an output coupled to a first input of means for controlling an oscillator which in turn has an output.
An oscillator is coupled to the output of the means for controlling a voltage controlled oscillator and has an output coupled to an input of the means for controlling an oscillator