Method and apparatus for clock distribution and for distributed clock synchronization

A method of phase synchronizing a plurality of spatially distributed application modules having synchronizing clocks requiring synchronization, each said application modules being connected, at a predetermined site nearest said module, to an outgoing path and, at a corresponding site nearest said module, to a return path of a pulse reference path, said method comprising the steps of:

• injecting reference pulses at a predetermined frequency into an injection site of said reference path such that said pulses travel along said outgoing path to a remote site and return to said injection site along said return path;
• determining, for each said application module, the time interval for each said pulse to travel from said predetermined site to said corresponding site associated with said application module;
• monitoring for each said application module the elapsed time interval for each said pulse to travel between said predetermined and corresponding sites associated with said application module;
• producing for each said application module a local phase reference signal when said elapsed time interval is one-half a last determined one of said time intervals;
• and synchronizing said clock of each said application modules with said local phase reference signal.

An electronic system comprising:

• a signal source for providing an initial signal;
• a plurality of receivers, each having a first and second input lead, each of said receivers requiring the use of an associated one of a plurality of locally generated signals, each of said plurality of locally generated signals corresponding to said initial signal and delayed from said initial signal by a
• a signal path having an end for receiving said initial signal, each of said first input leads of said plurality of receivers being connected to said signal path at an associated one of a first plurality of locations along said signal path such that each of said receivers has an associated first propagation delay between said source and said location, such that said first propagation delays are not equal, and each of said second input leads of said plurality of receivers being connected to said signal path at an associated one of a second plurality of locations along said signal path such that each of said receivers has an associated second propagation delay between said source and said location, such that said second propagation delays are not equal;
• and
• a plurality of means, each association with one of said receivers for combining said signals on said first and second input leads in order to generate a locally generated signal corresponding to said initial signal and having a propagation delay from said initial signal which is equal to the average of said first propagation delay and said second propagation delay associated with said receiver.

Apparatus for providing a signal comprising:

• a first input lead for receiving a first signal corresponding to an initial signal and delayed from said initial signal by a first propagation delay;
• a second input lead for receiving a second input signal corresponding to said initial signal and delayed from said initial signal by a second propagation delay;
• an output lead for providing a locally generated signal corresponding to said initial signal and delayed from said initial signal by a third propagation delay which is a function of said first and second propagation delays;
• a first phase detector for providing a first phase comparison signal indicative of the phase relationship between said first input signal and said locally generated signal;
• a second phase detector for providing a second phase comparison signal indicative of the phase relationship between said second input signal and said locally generated signal;
• means for combining said phase comparison signal to provide a combined phase comparison signal;
• and
• a voltage controlled oscillator for providing said locally generated signal in response to said combined comparison signal.