High-speed synchronous clock generated by standing wave

• US 5,990,721 A
• Filed: 08/18/1997
• Issued: 11/23/1999
• Est. Priority Date: 08/18/1997
• Status: Expired due to Term

• Current Assignee: Teradata US, Inc. (Teradata Corporation)
• Original Assignee: NCR Corporation
• Inventors: Mellitz, Richard I.
• Primary Examiner(s): Wambach, Margaret R.
• Application Number:
  US08/914,608
• Time in Patent Office: 827 Days
• Field of Search: 331/55, 331/49, 333/20, 307/1, 340/310.01, 327/262, 327/268, 327/271, 327/292, 327/295, 327/14
• US Class Current: 327/292
• CPC Class Codes: G06F 1/10 Distribution of clock signals , e.g. skew

Abstract

A clock for digital devices. Ordinarily, when multiple digital devices are clocked by a common clock, the clock signals frequently arrive at the digital devices at different times, due to propagation delays. The devices are thus not clocked synchronously. Under the invention, the multiple devices are connected to a common transmission line. A standing wave is generated on the transmission line, and the periodic collapse of the standing wave is used to clock the devices. Synchronous clocking to within about 1.0 nano-seconds has been attained, in a transmission line about ten feet long, wherein a clock signal ordinarily takes about 15 nanoseconds to travel from one end to the other.

Claims

1. A system comprising:

a) two transmission lines, each carrying a sinusoid;

b) means for deriving an oscillating signal from the two sinusoids; and

c) digital apparatus which is clocked by the oscillating signal.

11. System according to claim 1, wherein each sinusoid is less than 100 milli-volts, peak-to-peak.

12. System according to claim 1, wherein each sinusoid is less than 10 milli-volts, peak-to-peak.

13. System according to claim 1, wherein each sinusoid is less than 100 micro-volts, peak-to-peak.

14. System according to claim 1, wherein each sinusoid is less than 10 micro-volts, peak-to-peak.

2. A system comprising:

a) two transmission lines;

b) means for producing a sinusoidal signal on both transmission lines;

c) means for tapping a signal from each transmission line;

d) means for normalizing the tapped signals, so that the tapped signals represent sinusoids of similar amplitude; and

e) means for adding the normalized tapped signals together.

3. System according to claim 2, and further comprising:

f) digital apparatus for receiving the added signals, and using the added signals as a clock signal.

15. System according to claim 2, wherein each sinusoidal signal is less than 100 milli-volts, peak-to-peak.

16. System according to claim 2, wherein each sinusoidal signal is less than 10 milli-volts, peak-to-peak.

17. System according to claim 2, wherein each sinusoidal signal is less than 100 micro-volts, peak-to-peak.

18. System according to claim 2, wherein each sinusoidal signal is less than 10 micro-volts, peak-to-peak.

4. A system comprising:

a) first and second transmission lines;

b) means for producing first and second sinusoidal signals on the respective transmission lines;

c) a first phase locked loop, coupled to the first sinusoidal signal, for generating a first output sinusoid which is in substantially constant phase relation with the first sinusoidal signal;

d) a second phase locked loop, coupled to the second sinusoidal signal, for generating a second output sinusoid which is

i) in substantially constant phase relation with the second sinusoidal signal;

ii) of substantially the same peak-to-peak magnitude as the first output sinusoid; and

e) means for adding the first and second output sinusoids together.

5. A digital apparatus, comprising:

a) a transmission line having two entry ports;

b) launching means for launching a sinusoidal signal into each entry port;

c) suppression means for suppressing reflections of the sinusoidal signals within the transmission line; and

d) taps, at a plurality of points along the transmission line, each for deriving a clock signal from a standing wave produced by the sinusoidal signals.

6. Apparatus according to claim 5, in which the sinusoids have a base component of frequency, and no harmonic components of magnitude greater than 10 percent of the base component.

7. Apparatus according to claim 5, in which the sinusoids are time-synchronous.

8. In a printed circuit board, the improvement comprising:

a) digital circuits which require clock signals;

b) an elongated conductive trace;

c) means for generating a standing wave in said trace; and

d) means for picking off clock signals at selected locations on said trace, and delivering said clock signals to said digital circuits.

9. Improvement according to claim 8, in which all clock signals delivered to said digital circuits are synchronous to within 1.0 nano-second.

10. Improvement according to claim 8, in which the conductive trace is more than 18 inches long.