Method and apparatus for clock distribution and for distributed clock synchronization
DCFirst Claim
1. A clock distribution apparatus for use in providing a common absolute time reference to spatially distributed application modules requiring synchronized clocks, said apparatus comprising:
- means for transmitting an outgoing reference signal from a first site to a second site and a return reference signal from said second site to said first site upon arrival of said outgoing reference signal at said second site; and
means at each said application module for detecting an outgoing reference signal and a corresponding return reference signal and producing a local phase reference signal approximately midway through the time interval required for said outgoing reference signal to travel from a signal detecting site at said application module to said second site and said return reference signal to travel from said second site to said signal detecting site.
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Abstract
A method and apparatus of phase synchronizing a plurality of spatially distributed application modules having synchronizing clocks requiring synchronization, each application module being connected, at a predetermined site nearest the module, to an outgoing path and, at a corresponding site nearest the module, a return path of a pulse reference path, the method comprising the steps of injecting reference pulses at a predetermined frequency into an injection site of the reference path such that the pulses travel along the outgoing path to a remote site and return to the injection site along the return path; determining, for each application module, the time interval for each pulse to travel from the predetermined site to the corresponding site associated with the application module; monitoring, for each application module, the elapsed time interval for each pulse to travel between the predetermined and corresponding sites associated with the application module; producing, for each application module, a local phase reference signal when the elapsed time interval is one-half a last determined one of the time intervals; and synchronizing the clock of each application module with the local phase reference signal.
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Citations
54 Claims
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1. A clock distribution apparatus for use in providing a common absolute time reference to spatially distributed application modules requiring synchronized clocks, said apparatus comprising:
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means for transmitting an outgoing reference signal from a first site to a second site and a return reference signal from said second site to said first site upon arrival of said outgoing reference signal at said second site; and means at each said application module for detecting an outgoing reference signal and a corresponding return reference signal and producing a local phase reference signal approximately midway through the time interval required for said outgoing reference signal to travel from a signal detecting site at said application module to said second site and said return reference signal to travel from said second site to said signal detecting site. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 50, 51)
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37. A method of phase synchronizing a plurality of spatially distributed application modules having synchronizing clocks requiring synchronization, said method comprising the steps of:
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transmitting an outgoing reference signal from a first site to a second site and a return reference signal from said second site to said first site upon arrival of said outgoing reference signal at said second site; and detecting an outgoing reference signal and a corresponding return reference signal and producing a local phase reference signal approximately midway through the time interval required for said outgoing reference signal to travel from a signal detecting site at said application module to said second site and said return reference signal to travel from said second site to said signal detecting site. - View Dependent Claims (38, 39, 40, 41, 42)
- 40. A method as defined in claim 37, said predetermined frequency being less than or equal to
- space="preserve" listing-type="equation">f.sub.pulser =f.sub.hs /[floor}f.sub.hs 2D/v}]
where; fhs is the frequency of the high-speed system clock; floor {arg} is a function that takes the largest integer less than {arg}; D is the length of said outgoing path; v=kc=propagation velocity; k<
1; andc is the propagation velocity of light in a vacuum.
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41. A method as defined in claim 37, further including the step of regenerating each said reference pulse at said remote site.
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42. A method as defined in claim 37, further including the step of terminating and regenerating each said reference signals at the location of each application module extracting synchronism from said signals.
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43. 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:
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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. - View Dependent Claims (44, 45, 46, 47, 48, 49)
- 46. A method as defined in claim 43, said predetermined frequency being less than or equal to
- space="preserve" listing-type="equation">f.sub.pulser =f.sub.hs /[floor[f.sub.hs 2D/v}]
where; fhs is the frequency of the high-speed system clock; floor {arg} is a function that takes the largest integer less than {arg}; D is the length of said outgoing path; v=kc=propagation velocity; k<
1; andc is the propagation velocity of light in a vacuum.
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47. A method as defined in claim 43, further including the step of regenerating each said reference pulse at said remote site.
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48. A method as defined in claim 43, further including the step of terminating and regenerating each said reference pulses at the location of each application module extracting synchronism from said reference path.
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49. A method as defined in claim 43, said outgoing and return paths having equal lengths from any point thereon to the ends thereof.
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52. An electronic system comprising:
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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. - View Dependent Claims (53)
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54. Apparatus for providing a signal comprising:
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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.
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Specification