Distributing Frequency References

• US 20080068103A1
• Filed: 08/18/2006
• Published: 03/20/2008
• Est. Priority Date: 08/18/2006
• Status: Active Grant

• Current Assignee: Keysight Technologies, Inc.
• Original Assignee: Agilent Technologies, Inc.
• Inventors: Cutler, Robert T
• Granted Patent: US 7,589,595 B2
• Time in Patent Office: Days
• US Class Current: 331/74
• CPC Class Codes: H04J 3/0667 Bidirectional timestamps, e.g. NTP or PTP for compensation of clock drift and for compensation of propagation delays arrangements for monitoring round trip delays in packet switching networks H04L43/0864
• CPC Class Codes: H04J 3/0697 Synchronisation in a packet node

Abstract

Network aware oscillator synchronization via a computer network. A correction processor connected to an oscillator uses precision timing signals propagated over a digital network to generate an error signal. IEEE-1588 time synchronization protocols produce precision time signals which are converted to precision interval signals. In one embodiment a correction processor uses the precision interval signals to count pulses of the oscillator. A correction circuit compares the counter output with a predetermined value and generates an error signal. The error signal may be used to correct the oscillator, as in a voltage controlled oscillator. Or, the error signal may be propagated to consumers of the oscillator. This error signal, for example, may be used to correct an instrument display. An arbitrary reference oscillator may be used to generate the precision timing signals propagated on the network, slaving other oscillators to it. The precision of the reference oscillator may be deliberately overstated to insure it is used as a master.

Claims

1. A network aware oscillator comprising:

a network interface for receiving precision time messages from a digital network and producing precision time signals,

an oscillator producing a periodic output signal,

a timing converter converting the precision time signals to interval signals,

a counter gated by the interval signals and driven by the periodic output signal of the oscillator, and

an error generator comparing the output of the counter to a predetermined value producing an error signal.

2. The network aware oscillator of claim 1 where the oscillator has a frequency control input and the error signal drives the frequency control input to correct the oscillator frequency.

3. The network aware oscillator of claim 2 where the error signal is an analog signal.

4. The network aware oscillator of claim 2 where the oscillator is a voltage controlled crystal oscillator.

5. The network aware oscillator of claim 2 where the oscillator is temperature stabilized.

6. The network aware oscillator of claim 2 where the oscillator is a YIG tuned oscillator.

7. The network aware oscillator of claim 2 where the oscillator is a dielectric resonant oscillator (DRO).

8. The network aware oscillator of claim 2 where the error signal is propagated to consumers of the oscillator output.

9. The network aware oscillator of claim 8 where the error signal is a digital signal.

10. The network aware oscillator of claim 2 where the error signal corrects for oscillator frequency error and oscillator aging.

11. A method of operating a network aware oscillator comprising:

receiving precision timing signals from a digital network,

converting precision timing signals to interval signals,

counting the output of an oscillator gated by the interval signals, and

generating an error signal from the comparison of the counter output with a predetermined value.

12. The method of claim 11 further comprising:

driving a frequency control input of the oscillator using the error signal.

13. The method of claim 11 further comprising:

temperature stabilizing the oscillator.

14. The method of claim 11 further comprising:

propagating the error signal to consumers of the oscillator output.

15. The method of claim 11 further comprising:

generating a reference signal in an external reference oscillator,

generating precision timing signals from the reference oscillator, and

propagating the precision timing signals on the digital network.

16. The method of claim 15 further comprising overstating the accuracy of the reference in the precision timing signals propagated on the digital network.