Generation of topology independent reference signals

• US 4,998,262 A
• Filed: 10/10/1989
• Issued: 03/05/1991
• Est. Priority Date: 10/10/1989
• Status: Expired due to Term

• Current Assignee: Agilent Technologies, Inc.
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Wiggers, Hans A. M.
• Primary Examiner(s): Olms, Douglas W.
• Assistant Examiner(s): Chin, Stephen
• Application Number:
  US07/419,345
• Time in Patent Office: 511 Days
• Field of Search: 375/36, 375/38, 375/106, 375/107, 375/118, 375/10, 455/27, 455/49, 455/51, 328/55, 328/58, 328/72, 370/108, 371/1, 307/262, 307/511
• US Class Current: 375/356
• CPC Class Codes: H03L 7/07 using several loops, e.g. for redundant clock signal generation
• CPC Class Codes: H04L 7/0008 Synchronisation information channels, e.g. clock distribution lines

Abstract

A method and structure for providing plurality signals which are substantially synchronous at a plurality of distant points within a system is approached from a different point of view. Rather than employing a plurality of delays for adding various delay times to certain leads carrying the signal in question, in accordance with the teachings of this invention two separate leads are used to route such a signal within a system. The receiving circuitry are connected to the two leads carrying the signal in opposite order, that is the first receiver connected to the first lead is the last receiver connected to the second lead, the second receiver connected to the first lead is the next to last receiver connected to the second lead, and so on. In this manner, the average of the propagation delays between the first and second leads at any given receiver is substantially equal. A locally derived signal is generated for each of the receivers based upon the two signals provided by the source. Each of the locally generated signals are substantially synchronized. In one embodiment, a novel circuit is employed to generate a local signal for application to a particular receiver which includes a phase lock loop employing two phase detectors, one for comparing the phase of each of the two signals provided by source at the location of the receiver in question.

Claims

1. An electronic system comprising:

a signal source for providing an initial signal;

a plurality of 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 predefined time;

a forward path having an end for receiving said initial signal, each of said plurality of receivers being located at an associated one of a plurality of locations along said forward path such that each of said receivers has an associated forward propagation delay between said source and said location, such that said forward propagation delays are not equal;

a backward path having an end for receiving said initial signal, each of said plurality of receivers being located at an associated one of a plurality of locations along said backward path such that each of said receivers has an associated backward propagation delay between said source and said location, such that backward propagation delays are not equal; and

a plurality of means, each associated with one of said receivers, for combining the initial signal as received by that receiver through the forward path with the signal as received by that receiver through the backward path 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 forward propagation delay and said backward propagation delay associated with said receiver.

2. A system as in claim 1 wherein the sum of the distances along the forward and backward paths between said source and each of said receivers is substantially equal.

3. A system as in claim 2 wherein the total number of receivers is N, the locations along the forward path are designated from 1 to N beginning with the location closest to the end that receives the initial signal, the locations along the backward path are designated from 1 to N beginning with the location closest to the end that receives the initial signal, M is an integer not less than 1 nor greater than N, and a receiver which is located at the Mth position on the forward path is located at the (N+1-M)th position on the backward path.

4. 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 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 first and second phase comparison signals 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.

5. 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 predefined time;

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.

6. A system as in claim 5 wherein, for each receiver, the sum of the distances between said source and said first and second locations associated with said receivers is substantially equal to such sum associated with each other receiver.